• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.9
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• pp.741-749
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• 2012

Ad Hoc Self-Organizing TDMA (ASO-TDMA) has been proposed as a specification to support the multi-hop data communication service for ships over VHF band. It allows for organizing a multi-hop ad-hoc network in a distributed manner by sharing the radio resources among the ships navigating along the route. In this paper, Markov chain analysis is given to provide the average throughput performance for ASO-TDMA protocol Furthermore, the analytical results are verified with computer simulation, which shows that there exists the optimal transmission rate to maximize the average throughput as the subframe size and the number of ships are varying in each hop region.

• The Journal of the Acoustical Society of Korea
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• v.13 no.1E
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• pp.25-36
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• 1994

A problem of making a neural network learning self-adaptive to the training set supplied is addressed in this paper. This arises from the aspect in choice of an adequate stepsize for the update of the current weigh vectors according to the training pairs. Related issues in this attempt are raised and fundamentals in neural network learning are introduced. In comparison to the most popular back-propagation scheme, the usefulness and superiority of the proposed weight update algorithm are illustrated by examing the identification of unknown nonlinear systems only from measurements.

• Journal of Korean Library and Information Science Society
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• v.23
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• pp.29-77
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• 1995

The purpose of this study is to investigate the effectiveness and value of reading, the role of reading for character building and reading education for the character building instruction. A great book can change a person's life and future. Especially, reading in the juvenile period is important because of their intellectual curiosity and sensitivity. The results of the study were as follows. (1) In order to solve the problem of the dehumanization, and the confusion of the sense of value among young adults, we should enrich and cultivate the character of young adults through the reading education. (2) The effects of reading for personality are verbal effects, experimental effects, cultural effects, reformational effects and recreational effects etc. (3) The value of reading in the past were inspiration, information and recreation. But, in recent times, the interest in therapeutic value of reading is increasing. The theraputic value of reading is identification, catharsis and insights of one's problem through the character in the works. (4) The role of reading for the character building are the assistance of self-realization, the promotion of self-regulation and the assistance of self-understanding. (5) Psychological needs causing reading activity are the desire to escape from reality, better socialization, recreation and pleasure. (6) The mechanism of character building through the reading are the enlargement of experience, better adjustment to the environment and the society. (7) Reading education for the solution of developmental tasks of the young adults is important. The standard reading lists of Japan Reading Society, the list compiled by Lee Kyung-Sik and the list of Park Yong Doo are the example of the selected reading list for the solution of developmental tasks.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.2134-2143
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• 2018

This work introduces a fault diagnosis method for transformer based on self-powered radio frequency identification (RFID) sensor tag and improved Hilbert-Huang transform (HHT). Consisted by RFID tag chip, power management circuit, MCU and accelerometer, the developed RFID sensor tag is used to acquire and wirelessly transmit the vibration signal. A customized power management including solar panel, low dropout (LDO) voltage regulator, supercapacitor and corresponding charging circuit is presented to guarantee constant DC power for the sensor tag. An improved band restricted empirical mode decomposition (BREMD) which is optimized by quantum-behaved particle swarm optimization (QPSO) algorithm is proposed to deal with the raw vibration signal. Compared with traditional methods, this improved BREMD method shows great superiority in reducing mode aliasing. Then, a promising fault diagnosis approach on the basis of Hilbert marginal spectrum variations is brought up. The measured results show that the presented power management circuit can generate 2.5V DC voltage for the rest of the sensor tag. The developed sensor tag can achieve a reliable communication distance of 17.8m in the test environment. Furthermore, the measurement results indicate the promising performance of fault diagnosis for transformer.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.364-371
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• 2021

A magnetic flux saturation model of Synchronous Reluctance Motors (SynRMs) and a parameter estimation method are proposed at standstill. The proposed magnetic flux model includes the nonlinear relationship between the current and the magnetic flux for self-saturation and cross-saturation. Voltage is injected at standstill to estimate the magnetic flux saturation model. Voltages are injected into the d-axis and q-axis to obtain data on self-saturation. Subsequently, voltages are simultaneously injected into the d-q axis to obtain data on cross-saturation. On the basis of the measured current and the calculated magnetic flux, the parameters of the proposed model are estimated using the least square method (LSM). Simulation and experiment were performed on a 1.5-kW SynRM to verify the proposed method. The proposed model can be used to create a high-efficiency operation table, a sensorless algorithm, and a current controller to improve the control performance of a motor.

• Structural Engineering and Mechanics
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• v.86 no.2
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• pp.181-195
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• 2023

To predict the rheological behaviours along with the compressive strength of self-compacting concrete that incorporates environmentally friendly ingredients as cement substitutes, a comparative evaluation of machine learning methods is conducted. To model four parameters, slump flow diameter, L-box ratio, V-funnel time, as well as compressive strength at 28 days-a complete mix design dataset from available pieces of literature is gathered and used to construct the suggested machine learning standards, SVM, MARS, and Mp5-MT. Six input variables-the amount of binder, the percentage of SCMs, the proportion of water to the binder, the amount of fine and coarse aggregates, and the amount of superplasticizer are grouped in a particular pattern. For optimizing the hyper-parameters of the MARS model with the lowest possible prediction error, a gravitational search algorithm (GSA) is required. In terms of the correlation coefficient for modelling slump flow diameter, L-box ratio, V-funnel duration, and compressive strength, the prediction results showed that MARS combined with GSA could improve the accuracy of the solo MARS model with 1.35%, 11.1%, 2.3%, as well as 1.07%. By contrast, Mp5-MT often demonstrates greater identification capability and more accurate prediction in comparison to MARS-GSA, and it may be regarded as an efficient approach to forecasting the rheological behaviors and compressive strength of SCC in infrastructure practice.

• Korean journal of communication and information
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• v.17
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• pp.37-60
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• 2001

This study attempted to demonstrate the interaction effects between attitudinal frames of nine daily newspapers and community structure in the 1994s Michigan gubernatorial election. It was theoretically guided by framing research and the self-presentation theory of social-cognition perspective and empirically tested with archival data. For the purpose of this study, content analysis of nine statewide daily newspapers was employed in order to provide data on news framing. Data on voting rates for John Engler, winner of the 1994 Michigan Gubernatorial election, in each county of Michigan were used for vote choice while Michigan census data were used for constructing an Index of community structural differentiation. The results indicated that majority compliance frames were slightly more related with vote choice in homogeneous com-unities rather than were majority compliance frames in heterogeneous communities while social identification frames tended to have an influence on vote choice in heterogeneous communities more than did social identification frames in homogeneous communities.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.3
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• pp.1-7
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• 2007

RFID ( Radio Frequency IDentification ) is an automatic realization technology that recognizes things or a person with data stored tag, card, label, etc that have microchip by using radio frequency. Automation and efficient data base management(DBM) of system are possible by replaces using Bar-code that is used widely with using RFID. In this paper, we designed RFID tag data format that used to recognize information of books in Library and implemented library management system. Library management system is divided checking collection of books, self-loaning books system, self-returning books system, management books information system for a librarian. RFID leader realized information of tag and transfer it to host computer through RS-232 interface. Host computer processes and operates information with middleware. System that we made is depending on executive system for a librarian.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.2
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• pp.293-303
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• 2017

FIDO(Fast IDentity Online) technology is expanding very rapidly which can replace traditional password-based authentication with biometrics technology[1,7]. FIDO provides convenient authentication with biometrics technology and secure key management with smart card technology, but it does not provide user identification, thus traditional user identification technology should be used before a FIDO device is registered to a FIDO server. K-FIDO[3] is an approach to implement FIDO and certificate-based authentication technology into a single device that user can utilize certificate-based authentication in initial registration of FIDO device to FIDO server. It is expected that very shortly users will own and use multiple K-FIDO devices. If we consider the traditional approach of copying single certificate to multiple devices or issuing independent certificate to each device, there will be many complex problems. In this paper we propose more secure and convenient key management technology in multiple K-FIDO device scenario using self-extended certification[4].

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.501-512
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• 2018

Radio frequency identification (RFID) sensor tag provides several advantages including battery-less operation and low cost, which are suitable for long-term monitoring. This paper presents a self-powered RFID temperature sensor tag for online temperature monitoring in substation. The proposed sensor tag is used to measure and process the temperature of high voltage equipments in substation, and then wireless deliver the data. The proposed temperature sensor employs a novel phased-locked loop (PLL)-based architecture and can convert the temperature sensor in frequency domain without a reference clock, which can significantly improve the temperature accuracy. A two-stage rectifier adopts a series of auxiliary floating rectifier to boost its gate voltage for higher power conversion efficiency. The sensor tag chip was fabricated in TSMC $0.18{\mu}m$ 1P6M CMOS process. The measurement results show that the proposed temperature sensor tag achieve a resolution of $0.15^{\circ}C$/LSB and a temperature error of $-0.6/0.7^{\circ}C$ within the range from $-30^{\circ}C$ to $70^{\circ}C$. The proposed sensor tag achieves maximum communication distance of 11.8 m.