• Journal of Power Electronics
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• v.19 no.1
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• pp.108-118
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• 2019

This paper proposes a DC-link voltage balance controller using the fourth-phase of a three-level neutral-point clamped (NPC) PWM converter with medium vector selection (MVS) PWM for common-mode voltage reduction. MVS PWM makes the voltage reference by synthesizing the voltage vectors that cannot generate common-mode voltage. This PWM method is effective for reducing the EMI noise emitted from converter systems. However, the DC-link voltage imbalance problem is caused by the use of limited voltage vectors. Therefore, in this paper, the effect of MVS PWM on the DC-link voltage of a three-level NPC converter is analyzed. Then a proportional-derivative (PD) controller for the DC-link voltage balance is designed from the DC-link modeling. In addition, feedforward compensation of the neutral point current is included in the proposed PD controller. The effectiveness of the proposed controller is verified by experimental results.

• Electronics and Telecommunications Trends
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• v.36 no.1
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• pp.81-88
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• 2021

Post COVID-19, the medical legacy system will be transformed for utilizing medical resources efficiently, minimizing medical service imbalance, activating remote medical care, and strengthening private-public medical cooperation. This can be realized by achieving an entire medical paradigm shift and not simply via the application of advanced technologies such as AI. We propose a medical system configuration named "Medical AI Hub" that can realize the shift of the existing paradigm. The development stage of this configuration is categorized into "AI Cooperation Hospital," "AI Base Hospital," and "AI Hub Hospital." In the "AI Hub Hospital" stage, the medical intelligence in charge of individual patients cooperates and communicates autonomously with various medical intelligences, thereby achieving synchronous evolution. Thus, this medical intelligence supports doctors in optimally treating patients. The core technologies required during configuration development and their current R&D trends are described in this paper. The realization of the central configuration of medical AI through the development of these core technologies will induce a paradigm shift in the new medical system by innovating all medical fields with influences at the individual, society, industry, and public levels and by making the existing medical system more efficient and intelligent.

• Korea Trade Review
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• v.47 no.1
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• pp.13-24
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• 2022

This study was conducted because the global economic downturn caused by COVID-19 caused a surge in logistics costs and it was no longer possible to predict logistics costs using existing methods. For this study, we made the assumption that economic indicators affect logistics cost. Chapter 2 examines the current status of the liner market and factors affecting logistics costs. Based on this, Chapter 3 collects independent and dependent variables to determine the analysis model. As the independent variable, economic indicators of major countries constituting the SCFI were selected, and the dependent variables were the SCFI Europe Index and the SCFI USA Index. In Chapter 4, a panel analysis was conducted based on this, and it was confirmed that major economic indicators had a negative (-) effect on SCFI. This is contrary to the existing research results, which can be attributed to the special situation caused by COVID-19 and the imbalance of demand and supply by region. The results of this study are meaningful in that they can predict long-term logistics cost volatility without analyzing supply and demand, and can be applied to other studies as well.

• Korea Journal of Hospital Management
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• v.29 no.1
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• pp.56-63
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• 2024

Purposes: This study aims to analyze the correlation with the current status of the medical resident application rate, physician's income, and non-benefit rates of majors in each specialty subject and to suggest implications. Methodology: First, it analyzes the correlation between the medical resident application rate by specialty subject and the income of physicians. Second, it analyzes the correlation between the income of specialists and the non-benefit rate for each specialty subject at the clinic level. Findings: First, a significant positive correlation was found between the medical resident application rate and the average physician's income for each specialty subject (r=.718, p<.01). Second, a significant positive correlation was observed between physician income at the practitioner level by medical specialty and the non-benefit rate (r=.726, p<.01). Practical Implications: In this study, the correlation between medical resident application rate by specialty subject and physician's income, non-payment and physician's income was confirmed. Choosing a department that is less risky and can earn higher income is a natural phenomenon, but it is necessary to adjust the physicians crowding phenomenon to a specific specialty subject at the government level to maintain the medical system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.121-127
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• 2017

From the perspective of commercializing rotating machines equipped with magnetic bearings, maintaining the error between the mechanical center and the magnetic center within an acceptable level is crucial. The existing method of measuring the center error is to adjust the position references that minimize the current imbalance present in levitation control outputs. However, this method can be applied only after all the components of the system are operational. In this paper, we present a new method of estimating the center error by using only the position sensors and a current source. A force model that relates the position of the rotor with the coil currents is set up. Using this model, the center error is estimated by minimizing the difference between the force angles and the contact angles measured in a pull test. The feasibility of the method is numerically and experimentally validated.

• Journal of Nutrition and Health
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• v.33 no.2
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• pp.158-166
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• 2000

The effects of smoking and physical exercise on the plasma concentrations of lipid-soluble antioxidants were investigated in 62 healthy males, aged 34-65 years. Current smokers (n=21) and ex-smokers(n=16) had significantly lower plasma levels of carotenoids ($\alpha$-carotene, $\beta$-carotene, cryptoxanthin and lycopene), $\alpha$-tocopherol and ${\gamma}$-tocopherol than non-smokers (n=25). Plasma concentrations of retionl and ubiquinone (coenzyme Q10) were lower among ex-smokers and current smokers than among non-smokers, but the differences were not statistically significant. Regular physical exercise was associated with increased plasma levels of lipid-soluble antioxidants. Plasma concentrations of crytoxanthin, retinol and ubiquinone were significantly elevated in the group engaging in moderate amounts of exercise (more than 20 minutes per day) compared to the group engaging in small amounts of exercise (less than 10 minutes per day). Plasma $\alpha$-carotene, $\beta$-carotene, lycopene levels in the subjects were affected more by smoking than by exercise. However, plasma levels of cryptoxanthin, retinol and ubiquinone in the subjects were affected more by exercise than by smoking. These findings suggest than smoking may cause a decrease in plasma lipid-soluble antioxidants during neutralization of reactive oxygen species present in cigarette smoke and that poor exercise habits may accelerate this imbalance of oxidant/antioxidant homeostasis in middle-aged Korean men.

• Journal of Digital Convergence
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• v.13 no.1
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• pp.111-124
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• 2015

The economic growth in China takes the step of the Internet/Mobile revolution together. The high internet penetration provided the opportunity to increase the e-commerce market with fast speed. However, due to imbalance of the growth speed and preparation, the problems on various infrastructures and regulations were generated. Therefore, this study investigateed the current status of e-commerce market and sub-categories. This study also discussed about the problem of e-commerce logistics system, consumer protection, R&D investment, and human resources and provided the considerations for the future improvement. Finally, this study diagnosed the mobile payment and internet finance market and new e-commerce tax regulation, and then suggested institutional implications for the international standardization. This study is meaningful to provide the first implication to the Korean exporters after Chinese government had announced market open strategy for the 5 year e-commerce development plan.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.5
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• pp.248-254
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• 2001

The traction power demand highly varies with time and train positions and the traction load is a large-capacity current at single phase converted from 3-phase power system. Subsequently, each phase current converted from 3-phase power system cannot be maintained in balance any longer and thus the traction load can bring about imbalance in three-phase voltage. Therefore, the exact assessment of voltage unbalance must be carried out preferentially as well as load forecast at stages of designing and planning for electric railway system. The evaluation of unbalance voltage in areas, such as electric railway depots should be a prerequisite with more accuracy. The conventional researches on voltage unbalance have dealt with connection schemes of the transformers used in ac AT-fed electric railroads system and induced formulas to briefly evaluate voltage unbalance in the system(3). These formulas are still being used widely due to their easy applicabilities on voltage unbalance evaluation. Meanwhile, they don't take into account detailed characteristics of ac AT-fed electric railroads system, being founded on some assumptions. Accordingly. accuracy still remains in question. This paper proposes a new method to more effectively estimate voltage unbalance index. In this method, numerous diverted circuits in electric railway depots are categorized in three components and each component is defined as a two-port network model. The equivalent circuit for the entire power supply system is also described into a two-port network model by making parallel and/or series connections of these components. Efficiency and accuracy in voltage unbalance calculation as well can be promoted by simplifying the circuits into two-port network models.

• Journal of Environmental Science International
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• v.32 no.12
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• pp.915-923
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• 2023

The purpose of the study is to explore strategies to revitalize the distribution of landscaping plants in Gangwon State (hereinafter referred to as Gangwon-do). To understand the current distribution status and perception of landscape materials in Gangwon-do, a survey was conducted on producers and consumers focusing on cultivation area and method, cultivated species and quantity, purchase species and quantity, and purchase area. Producers often cultivated open land, and in the case of trees and shrubs, most of them cultivated <5 species. On the other hand, consumers preferred field cultivation products when purchasing trees and shrubs. Approximately 6-10 species of trees and shrubs were preferred for a single purchase, confirming an imbalance in the supply and demand of landscaping plants. In addition, both producers and consumers had a positive perception of landscape plant transactions in Gangwon-do; however, the dissatisfaction factors for producers included a small consumer base and difficulties for them in securing standards and quantities. Based on these results, it is necessary to establish a platform that can interconnect producers' landscape plant cultivation information with consumers' requirements to rejuvenate the landscape plant distribution market and enhance competitiveness in Gangwon-do. In addition, this platform is expected to have a positive impact on improving the quality of landscaping plants, setting reasonable prices, and increasing domestic demand in Gangwon-do by providing opportunities for cultivation, promotion, and marketing education through producer support projects.

• Convergence Security Journal
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• v.14 no.3_1
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• pp.35-44
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• 2014

It has been shown that the lack of sufficient defense industry cooperation between Korea and the US. The severe imbalance in defense trade between tow countries and Korea's weak defense industrial base has been a problem. This paper suggests the enhancement of defense industry cooperation with the US as a defense policy. The US policy has been changed to utilize the globalization of defense industries. The following cases were analyzed to show the policy change; The security of supply arrangement with 6 countries, the defense cooperation treaty with the United Kingdom and Australia. the defense Memorandum of Understanding with 23 countries, and the international cooperation with 8 countries for F-35 JSF program. Korea government needs to sign a defense MOU with U.S. and the defense industries are recommended to increase the opportunities of weapon system co-development and co-production. So that the Korea defense industry may improve competitiveness and to overcome the current weaknesses.