• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.12
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• pp.689-697
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• 2005

In this paper, an application of a decentralized $H_{\infty}$ controller(DHC) to multiple controlled-permanent magnet(CMAG) magnetic levitation(Maglev) systems is presented. The designed DHC using two Riccati equations iteratively has simpler structure and needs less computational loads than conventional centralized $H_{\infty}$ controller. A target plant is a hybrid-type CMAG system with permanent magnet and coil, and its mathematical model is firstly derived to design the DHC. To implement the designed algorithm, a real Maglev vehicle system including digital controller, chopper, sensor, etc., is manufactured. To compare the performances of the DHC method with an observer-based state feedback control(OSFC), the input tracking and disturbance rejection characteristics are experimentally tested. As performance indices(PI), integral of squared error(ISE), integral of absolute error(IAE), integral of time multiplied by absolute error(ITAE) and integral of time multiplied by squared error(ITSE) are used. From the experimental results, it can be seen that the input tracking and disturbance rejection performances of the DHC are better than those of the conventional controller.

• Journal of Information Technology Applications and Management
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• v.26 no.6
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• pp.79-87
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• 2019

Blockchain is a distributed network in a decentralized P2P infrastructure. In this paper, we propose and implement a blockchain-based pet trade service DApp(Decentralized Application). In the existing trading services, there is no way to know the status of dogs in interpersonal transactions and an additional distribution cost has been incurred. As a solution to this problem, we introduce a blockchain technology for a pet trade service where users can check whether an individual pet is healthy or not by its registered biometric data in order to have an efficient and confident trade service. The registered users can purchase puppies or registering information for their dogs to sell through a pet trade service DApp. It is also possible to make a reliable trade by verifying whether the dog is actually the same one through an inscription information of a dog.

• Journal of the Korean Institute of Landscape Architecture
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• v.32 no.2
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• pp.78-85
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• 2004

To manage rainwater environmentally friendly, it is necessary to let the rainwater be infiltrated naturally and make reservoirs to detain it in the chosen spot. Not only should it be prepared to handle the city flood, but also it be a necessary alternative for establishing the ecological water circular system in cities. Therefore, considering the present rainwater. management system, this study analysed the status of products which can be interchanged from existent systems to rainwater infiltrating systems. In this study, the infiltrating equipment that is applicable to the Korean drainage system was developed. The case was studied out to investigate the effects of infiltrating and the detaining ability of the developed product. The case site, block 6 of Sang-am residence, was selected and analyzed. The amount of infiltration and detention per unit of the introduced facilities, i.e., infiltrating pipes and tanks were calculated. In this research, the amount of each infiltrating tank was revealed to be 1.353 m/hr and the amount of detention as 0.299 m/hr. And the amount of each infiltrating pipe was found to be 0.541 m/hr and the amount of detention was 0.118 m/hr. To examine the effects of the system, the total amount of the outlet before and after installing was compared and calculated. In doing this, a basis for deciding the arrangement and number of tanks and pipes of the infiltrating system was made.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.5
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• pp.889-899
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• 2021

This paper proposes a reliable data sharing scheme on the internet of vehicles (IoV) by utilizing blockchain technology for constructing a decentralized system approach. In our model, to maintain the credibility of the information messages sent by the vehicles to the system, we propose a reputation rating mechanism, in which neighboring vehicles validate every received information message. Furthermore, we incorporate an incentive mechanism based on smart contracts, so that vehicles will get certain rewards from the system when they share correct traffic information messages. We simulated the IoV network using a discrete event simulator to analyze network performance, whereas the incentive model is designed by leveraging the smart contract available in the Ethereum platform.

• Journal of Internet Computing and Services
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• v.22 no.5
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• pp.27-33
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• 2021

With the broad adoption of the Internet of Things (IoT) in a variety of scenarios and application services, management and orchestration entities require upgrading the traditional architecture and develop intelligent models with ultra-reliable methods. In a heterogeneous network environment, mission-critical IoT applications are significant to consider. With erroneous priorities and high failure rates, catastrophic losses in terms of human lives, great business assets, and privacy leakage will occur in emergent scenarios. In this paper, an efficient resource slicing scheme for optimizing federated learning in software-defined IoT (SDIoT) is proposed. The decentralized support vector regression (SVR) based controllers predict the IoT slices via packet inspection data during peak hour central congestion to achieve a time-sensitive condition. In off-peak hour intervals, a centralized deep neural networks (DNN) model is used within computation-intensive aspects on fine-grained slicing and remodified decentralized controller outputs. With known slice and prioritization, federated learning communications iteratively process through the adjusted resources by virtual network functions forwarding graph (VNFFG) descriptor set up in software-defined networking (SDN) and network functions virtualization (NFV) enabled architecture. To demonstrate the theoretical approach, Mininet emulator was conducted to evaluate between reference and proposed schemes by capturing the key Quality of Service (QoS) performance metrics.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.6
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• pp.145-150
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• 2020

The importance of managing blind spots in the welfare crisis is increasing. Accordingly, in order to manage the blind spot of the welfare crisis, it is necessary to manage the social safety net with the contents of supporting income and self-reliance of low-income families, and actively discovering and supporting poor and crisis households. In this paper, we reviewed various problems related to blind spots for the management of welfare blind spots, and proposed the applicability of blockchain-based distributed ID and the possibility of distributed ID technology in stages by considering the range of blind spots.

• Journal of the Korea Society of Computer and Information
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• v.26 no.2
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• pp.69-78
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• 2021

In this paper, we propose a implementation plan of the human resource pool recruitment system using private (permitted) blockchain. The term Human Resource has become commonly used and has come to recognize human resources as resources. Despite these changes, the use of human resource pools has been sluggish. Once entered, information is often not updated on a regular basis and does not provide sharing, searching, carrier management and anti-counterfeiting. In this research, in order to provide a human resource pool recruitment system that utilizes private (permitted) blockchain, we first used the blockchain network to enable sharing and searching of human resource pools, and to use keywords. Used to get results that meet certain conditions. Second, we added an institutional verification process to ensure the integrity of the input data and prepared preventive measures in the non-technical part by utilizing the structural characteristics of the blockchain to prevent counterfeiting and alteration. Third, we designed and implemented a Dapp (Decentralized application) that includes a Web UI so that each of the three groups can control the blockchain and the predefined processes and business logic.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.3
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• pp.895-905
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• 2018

Public opinion polls have a strong influence on modern society as a means of examining the tendency of social groups on specific issues. As the influence of the polls increases, the problem of forgery and falsification of the results becomes an important issue. So, to guarantee the reliability of the results, our society needs novel mechanisms. As one of such mechanisms, the Ethereum blockchain is an environment for developing decentralized applications with the reliable blockchain technology. Ethereum decentralized applications can utilize smart contracts to provide services for users in transparent and reliable ways. In this paper, we propose a polling method that guarantees reliability using the blockchain technology, which is a distributed ledger technique that makes forgery or falsification actually impossible. The proposed method provides a robust verification function on the results of the associated polls for individual voters and verification organizations. Also, we present a distributed opinion polling application running on our private Ethereum blockchain network, showing the effectiveness of the proposed method.

• Journal of Korean Elementary Science Education
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• v.37 no.2
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• pp.206-218
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• 2018

The purpose of this study is to analyze the teaching behaviors and visual attention according to teacher's career in Elementary Science Inquire-based Class. Participants were four elementary school teachers in Seoul. They were all in grade 5 and taught science. According to the experience of elementary science education, two novice teachers and two expert teachers were identified. Participants taught Respiration in the 'Structure and Function of our Body' in the elementary science fifth grade. The mobile eye tracker used in this study is SMI's ETG 2w, which is a binocular tracking system. In addition, a video camera was installed behind the classroom to record the entire class. We recorded all the contents of the recorded video and analyzed the results. In this study, the actual practice time, participant's visual attention, and decentralized attention ability were analyzed by class phase. The results of the study are as follows. First, there was a difference between planned class time and actual practice time. The novice teachers were having difficulty in reconstructing the contents of education, and the expert teachers were reconstructing the curriculum and interacting with the students with high understanding and application of the curriculum. There were many differences between the novice teachers and the expert teachers in the tour guidance to confirm student activities. Second, if we look at the visual attention on the area related to teaching and learning by class phase, the novice teacher concentrates all the steps in a specific area, expert teachers showed an equal visual attention to meaningful areas of teaching and learning activities. Third, there was a statistically significant difference in activities 1-1, 1-2, 2-1, and 2-2 when the participants' decentralized attention ability. Expert teachers frequently checked students' understanding and interests. There was a lot of interaction with students. It is also shown through the decentralized attention ability that the novice teachers concentrate on a specific area, and the expert teachers have a high degree of decentralized attention ability and visual attention evenly.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.871-874
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• 2010

Needs for Smart Grid development are increasing all over the world as a solution to its problem according to depletion of energy resources, climatic and environmental rapidly change and growing demand for electrical power. Especially decentralized power is attracting world's attention. In this mood a new era for a unit scale of decentralized power environment is on its way in building. However there is a problem to have to be solved in the uniformity of power quality because the amount of power generated from renewable energy resources such as wind power and solar light is very sensitive to climate fluctuation. And thus this paper tries to suggest an energy management method on basis of real time monitoring for meteorological data. In the current situation of lacking in USN-based killer application in Smart Grid field, this paper proposes the USN-based DER management system which collects the meteorological data and control power system througout utilizing wireless sensor network technique this business. This communication technique is regarded to be efficient in aspects of installation cost and tits maintenance cost. The proposed EMS model embodies the method for predicting the power generation by monitoring and analyzing the climatic data and controling the efficient power distribution between the renewable energy and the existing power. The ultimate goal of this paper is to provide the technological basis for achieving zero-energy house.