• Journal of Power Electronics
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• v.11 no.6
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• pp.914-921
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• 2011

Commencing with incandescent light bulbs, every load today creates harmonics. Unfortunately, these loads vary with respect to their amount of harmonic content and their response to problems caused by harmonics. The prevalent difficulties with harmonics are voltage and current waveform distortions. In addition, Electronic equipment like computers, battery chargers, electronic ballasts, variable frequency drives, and switching mode power supplies generate perilous amounts of harmonics. Issues related to harmonics are of a greater concern to engineers and building designers because they do more than just distort voltage waveforms, they can overheat the building wiring, cause nuisance tripping, overheat transformer units, and cause random end-user equipment failures. Thus power quality is becoming more and more serious with each passing day. As a result, active power filters (APFs) have gained a lot of attention due to their excellent harmonic compensation. However, the performance of the active filters seems to have contradictions with different control techniques. The main objective of this paper is to analyze shunt active filters with fuzzy and pi controllers. To carry out this analysis, active and reactive current methods ($i_d-i_q$) are considered. Extensive simulations were carried out. The simulations were performed under balance, unbalanced and non sinusoidal conditions. The results validate the dynamic behavior of fuzzy logic controllers over PI controllers.

• Journal of Power Electronics
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• v.19 no.1
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• pp.179-189
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• 2019

Four-quadrant converters (4QCs) are widely used as AC-DC power conversion interfaces in many areas. A control delay commonly exists in the digital implementation process of 4QCs, especially for high power 4QCs with a low switching frequency. This usually results in alternating current distortion, increased current harmonic content and system instability. In this paper, the control delay is divided into a computation delay and a PWM delay. The impact of the control delay on the performance of a 4QC is briefly analyzed. To obtain a fundamental value of AC current that is as accurately as possible, a specific sampling method considering the PWM pattern is introduced. Then a current predictive control based on a modified z-transform is proposed, which is effective in reducing the control delay and easy in terms of digital implementation. In addition, it does not depend on object models and parameters. The feasibility and effectiveness of the proposed predictive current control method is verified by simulation and experimental results.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1260-1268
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• 2018

To improve fuel performance and specific characteristics of long storage and moving through fuel systems additives should be added in kerosene type aviation turbine fuel (AVTUR) such as antioxidant, fuel system icing inhibitor (FSII), electric conductivity improvers and so on. The dosage of additives has to be analyzed qualitatively and quantitatively due to inspect the quality of abnormal fuel and distinguish other petroleum products. Multi-dimensional GC-MS (MDGC-MS) with Deans switching technique are applied the determination of antioxidant and FSII, which are added with AVTUR containing complex mixture of hydrocarbons. Antioxidant and FSII in the range of 2.5-20 mg/L was quantitatively and qualitatively analyzed using MDGC-MS and the detection limit was about twice as low as that of the 1-dimensional GC-MS results. The method in this study has been higher peak resolution compared with GC-MS and could be simultaneously analyzed different two additives without sample pre-treatment.

• Food Science and Biotechnology
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• v.17 no.2
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• pp.262-266
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• 2008

This study was conducted to provide a vitamin $B_{12}$ database for the representative Korean food items and to assess the dietary intake assessment of vitamin $B_{12}$ for Koreans. The vitamin $B_{12}$ content of 106 foods had been determined by high performance liquid chromatography (HPLC) using column switching method. Rich sources of vitamin $B_{12}$ were meats, milk, and egg ($0.3-3.4\;{\mu}g/100g$). Vegetables and fruits contained vitamin $B_{12}$ below limit of detection (LOD). The major food sources for vitamin $B_{12}$ intake were milk (72.0%), meats (22.3%), egg (3.6%), and fishes & shellfishes (2.1%). Mean vitamin $B_{12}$ intake of Koreans was $3.16\;{\mu}g$/person/day. The proportion of population with intake below estimate average requirement (EAR) and above recommended intake (RI) of vitamin $B_{12}$ was 60.7 and 36.5%, respectively. The vitamin $B_{12}$ intake level of young children with 1-2 years which was 834.6% of RI while the intake level of the older adults 50 years and older was only 70.0% of RI. Also, there were regional differences between urban and rural area. The population with intake below RI was larger than that with intake above RI in Korea.

• The Journal of the Korea Contents Association
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• v.20 no.5
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• pp.58-68
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• 2020

In this paper, we simulated disaster broadcast service using terrestrial UHD additional data. We looked at nine functions(warning alarm, location-based information, multilingual, re-viewing the title of breaking news, evacuation knack video, CCTV, clip video, wake up, automatic channel switching) by referring to ATSC 3.0 standards. Analyzing the advantages and problems of the proposed disaster broadcast. Expert interviews were conducted after a demonstration and explanation of terrestrial UHD disaster broadcast. They said that the problems with the technology were difficulty in using, obstruction of viewing, content creation problems, and problems with advertisers. In addition to the lack of simulation-based research, this research has provided an insight into the technology by showing it in a visible way. This helped shape the advantages and problems of technology.

• Journal of the Korean Magnetics Society
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• v.4 no.3
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• pp.244-248
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• 1994

Magnetic and Magneto-optical characteristics of NdTbFeCo alloy films and NdTbFeCo/TbFeCo double-layered films have been investigated. It was observed that the Kerr rotation(${\theta}_{k}$) in the short wavelength region increased and the coercivity decreased as the substitutional amount of Nd for Tb in NdTbFeCo film at the constant FeCo content. In spite of the increased ${\theta}_{k}$, a small coercivity of NdTbFeCo film made this medium unsuitable for magneto-optical recording medium at short wavelength. An effort was made to improve coercivity by exchange coupling with TbFeCo film of high coercivity. In the exchange-coupled $Nd_{16.9}Tb_{15.2}Fe_{50.4}Co_{17.5}(150\;{\AA})/Tb_{21.1}Fe_{65.0}Co_{13.9}(300\;{\AA})$ double-layered film, the magnetization reversal switching field and the Kerr rotation angle were increased to about 6.0 KOe and $0.32^{\circ}$ at 500 nm, respectively. This result indicates that exchange-coupled NdTbFeCo/TbFeCo film can be a promising candidate for agneta-optical rerding medium short wavelenhth.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4B
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• pp.298-305
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• 2003

In this paper, we proposed a high performance lookup controller for IP packet forwarding engine of ATM based label edge routers. The lookup controller is designed to provide services such as MPLS, VPN, ELL, and RT services as well as the best effort. For high speed searching for IP addresses, we employed a TCAM based hardware search device not using traditional algorithmic approaches. We also implement lookup control functions into FPGA for fast processing of packet header and lookup control. The proposed lookup controller is designed to support differenciated services for users and to process in pipelined mechanism for performance improvement. A two-step search scheme is also applied to perform lookup for the key combined with multi-field of packet header. We found that the proposed lookup controller provides the performance of about 16M packets per second through simulations.

• Journal of Digital Convergence
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• v.17 no.10
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• pp.417-426
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• 2019

The purpose of this study is to analyze the success and failure of the movie made by the original game by comparing the box office environment of the movie made by the original game and to derive the necessary elements to make a good original movie. The specific analytical content studied the specific successes and failure factors of the remake of the game with , , and . Analyzes of the research show that the audience can be divided into game fan and non - game fans, and how to reflect the expectation on both sides of the movie is an important factor in making the movie. Also, games of different styles and genres from other themes can not be created in the same way as remixing movies, but flexible diversity and management are needed. Unconditional scenarios of games or game switching of movies can not be popular among the public, and it is very important to analyze specific target audiences.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.797-802
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• 2023

In an environment where English is a foreign language, English learners can use AI voice chatbots in English-speaking practice activities to enhance their speaking motivation, provide opportunities for communication practice, and improve their English speaking ability. In this study, we propose a teaching-style AI voice chatbot that can be easily utilized by lower elementary school students and enhance their learning. To apply the Teachable Agent system to language learning, which is an activity based on tense, context, and memory, we proposed a new method of TA by applying the Teachable Agent to reflect the learner's English pronunciation and level and generate the agent's answers according to the learner's errors and implemented a Teachable Agent AI chatbot prototype. We conducted usability evaluations with actual elementary English teachers and elementary school students to demonstrate learning effects. The results of this study can be applied to motivate students who are not interested in learning or elementary school students to voluntarily participate in learning through role-switching.

• Journal of vocational education research
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• v.37 no.5
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• pp.25-53
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• 2018

The purpose of this study is to find out the improvement plan through the satisfaction survey of the trainees involved in vocational training fraud preventive education. In order to do this, we conducted a satisfaction survey(4,263 persons) of 5,939 people who participated in the prevention education conducted by group education or e-learning in 2017. Finally we collected 4,237 effective responses data. Descriptive statistics and the regression analysis were conducted. The finding of the study were as follows. First, the education service quality(4.42), satisfaction level(4.44), understanding level(4.44) and help level(4.45) were significantly higher than those of participants in the preventive education 4 and above. Second, e-learning participants' perceived level of education service quality, satisfaction, comprehension, and help was higher in all variables than collective education's. Third, all of the sub-factors of preventive education service quality influenced satisfaction, understanding, and help in collective education and e-learning, respectively. In the collective education, the contents of education had the greatest influence, and in e-learning, the data composition had the greatest influence. Fourth, desirable education contents were cases of fraud training(70.7%), disposition regulations(47.9%), NCS course operation instructions(32.8%) and training management best practices(32.4%). Additional requirements also included the establishment of an in-depth course, the provision of anti-fraud education content for trainees, and screen switching and system stability that can be focused on e-learning. Therefore, this study suggests that first, it is necessary to activate e-learning for prevention education more, reflecting satisfaction of e-learning is higher than that of collective education. Second, it is necessary to diversify the content of preventive education and to provide it more abundantly, because it has the biggest influence in common with the satisfaction, understanding and help level of the preventive education. Third, education content next, the factors that have a relatively big influence on satisfaction are shown as delivery method and education place in the collective education. Therefore, it is necessary to prepare education place considering the assignment of instructor and convenience. Fourth, constructing data next, the factor that have a relatively great influence on understanding and help are found to be operator support, and more active operator support activities are required in e-learning. Fifth, it is required to delivery prevention activity for trainees participating in vocational training. Sixth, it is necessary to analyze the educational need to construct the contents of preventive education more systematically.