• Journal of Power Electronics
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• v.17 no.1
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• pp.31-40
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• 2017

A novel voltage-fed single-stage power factor correction (PFC) full-bridge converter based on asymmetric phase-shifted control for battery chargers is proposed in this paper. The attractive feature of the proposed converter is that it can operate in a wide output voltage range without an output low-frequency ripple, which is indispensable in battery charger applications. Meanwhile, the converter can maintain a high power factor and a controllable dc bus voltage over a wide output voltage range. In this paper, the realization of PFC and the operation principle of asymmetric phase-shifted control are given. A small-signal analysis of the proposed single-stage power factor correction (PFC) full-bridge converter is performed. Experimental results obtained from a 1kW experimental prototype are given to validate the feasibility of the proposed converter. The PF is higher than 0.97 over the entire output voltage range with the proposed control strategy.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.377-382
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• 2016

In 2013, a total capacity of 591.3 MW of installed wind power generation was achieved in Korea, with a total of 1,139 MWh of wind energy generated that year. More wind power plants will be installed in the coming years, and it is important to develop methods to reduce the output variability of these resources so as to provide stable power to the power grid of Korea. In this regard, this paper proposes the use of energy storage system (ESS) as a means to stabilize the output variability of wind power plants. Presented in this paper is a method that uses Discrete Fourier Transform (DFT) to determine the ESS capacity needed to provide a stable power output for ancillary services such as frequency regulation, economic dispatch, and emergency reserves. In the first step of the proposed method, four regions (namely, Samdal, Yeongdeok, Yeongyang, and Gangwon) in Korea that had the most wind power generation capacity were selected for analysis. In the second step, the individual and aggregated wind power outputs of the selected regions in 2013 were obtained This information was then used in the third step, where DFT analysis of the power outputs was used to drive the magnitudes of the output variation. And finally, the ESS capacity requirements needed to provide different ancillary services were determined based on the magnitudes of the output variation.

• Journal of Information Technology Services
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• v.17 no.1
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• pp.47-58
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• 2018

In this study, we define Fintech services as review previous literatures and identify the traditional Fintech service market for analysing the economic effects of the Fintech Industry by using the 2014 Input-Output Table. We can identify the current market of Fintech industry which consists of VAN, PG, financial SW, mobile banking and Fintech R&D and we conduct Input-Output analysis by using non-competitive import model. The Input-Output analysis results show that production inducement effect and front/rear chain effect of the Fintech Industry are below average of other industries. This is because the Fintech technology and industry were emerging in Korea at that time (2014), and thus the ripple effects are not significant. Especially, due to the existing white risk financial regulation, new business opportunities have not been open to adapt new ICT-financial technologies. Therefore, when the business ecosystem is build through deregulation and platforms of the financial sector, it is expected that the Fintech Industry will have a high ripple effect. In this study, we identify the current market of Fintech industry from ICT indusries and conduct Input-Output analysis. The economic effects of the Fintech industry are not remarkable, but it is significant to identify the emerging market and present the basic analysis of issued research field.

• Journal of the Korean Solar Energy Society
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• v.27 no.3
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• pp.23-28
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• 2007

In this study, we analyzed the maximum output power characteristics of crystalline silicon photovoltaic module by change of environmental effects. The electrical, optical and thermal property of PV modules were investigated during outdoor test period about 70 days. There was a fluctuation in maximum output power by change in transmittance caused by environment effects like rain, snow and dust. The effects of external environmental change were analyzed using climate data. Also local thermal temperature variation and transmittance imbalance on surface of PV module which might lead degradation of constituent material were detected using infrared camera. The further analysis is describe in the following paper.

• Current Photovoltaic Research
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• v.7 no.3
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• pp.71-75
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• 2019

Solar energy is one of the renewable energy sources. It can respond to expanding energy demand. A solar cell module is designed to have a durability that can be developed over a long period of 25 years to be installed outdoors and perform like a stable power supply. We need Standard Test Condition (STC)-based power output data before and after testing to measure the power output of existing modules. The modules are shown to reduce power output by comparing data before and after outdoor experiments regardless of whether they are indoor or outdoor. It is easy to compare the power output quantities through the module simulator in the indoor. However, it takes a lot of testing time and costs to compare the power output on outdoor in the case of a high number of modules and distance from the module simulator. It can save time and costs if we can check the power output using the data in outdoor. We have used the long-term outdoor test to find the elements out that corresponds to the reductions in power output quantities. We have conducted research that matched the actual and the tests.

• Journal of the Korean Society for information Management
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• v.32 no.3
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• pp.317-340
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• 2015

This study clarified the knowledge structure of international collaboration in psychiatry based on analyzing networks in order to construct cooperation networks for international collaboration in psychiatry in South Korea. The result of analysis of knowledge structure at a state-level is as follows. First, this study found that the rate of collaboration for five years is high as 89.97%. Moreover, this study investigated the change of rate of collaboration and international collaboration according to the passage of time, and ascertained that while the rate of international collaboration has increased, Second, this study examined the trend of research on collaboration between Asian countries, and found that collaboration between Asian countries is on a low level. Third, the country (or group) that the number of papers of international collaboration and the value of centrality are the highest is EU-28. The result of analysis of knowledge structure at a research output-level is as follows. this study analyzed the correlation of centrality with research output, and found that positive correlation exists in the three indicators of centrality, and a country with high centrality has good research output.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.498-501
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• 2012

A methodology to evaluate the performance analysis for micro hydropower sites has been studied. It consists of two main parts; flow duration function which can describe micro hydropower sites and performance analysis to estimate the output characteristics of micro hydropower plants. The output performance characteristics for Magok stream was analyzed, using developed model. Also, primary design specifications such as design flowrate, installed capacity, operational rate and annual electricity production were estimated and dicussed. Additionally, it was found that the developed model in this study is useful tool to estimate feasibility assessment for micro hydropower sites.

• Asia-Pacific Journal of Business
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• v.10 no.2
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• pp.1-12
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• 2019

Collaborative research and development (R&D) has been encouraged based on the belief that knowledge spill-over is mutually beneficial for partners. Although the benefits are supported by science and technology policy research, the risk of R&D collaboration has not been extensively discussed. Two independent studies suggest that there are risks associated with the overuse of collaborative research frameworks. Two sets of R&D collaboration data were analyzed: between the national bio-technology research program and 1) Data Envelop Analysis (DEA), and 2) between Stochastic Frontier Analysis (SFA). In the case of SFA, output measures were integrated into a single output, with weights extracted from research programme managers' responses to the questionnaire. While the DEA result demonstrated the inefficiency of collaborative research, SFA did not. Unlike previous research highlighting risks associated with disclosing proprietary R&D and potential conflict of interest, our study indicates that the transaction's social cost affects collaborative research efficiency. Therefore, governments promoting R&D collaborations should be carefully managed, and policy makers must reconsider the strict conditions governing compulsory collaborative R&D programs.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.4
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• pp.337-343
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• 2015

The multi-level inverters are highly efficient for high-power and medium-voltage AC driving applications, such as high-speed railway systems and renewable energy resources, because such inverters generate lower total harmonic distortion (THD) and electromagnetic interface (EMI). Lower switching stress occurs on switching devices compared with conventional two-level inverters. Depending on the multi-level inverter topology, the required components and number of switching devices are different, influencing the overall efficiency. Comparative studies of multi-level inverters based on loss analysis and output characteristic are necessary to apply multi-level inverters in high-power AC conversion systems. This paper proposes a theoretical loss analysis method based on piecewise linearization of characteristic curves of power semiconductor devices as well as loss analysis and output performance comparison of five-level neutral-point clamped, flying capacitor inverters, and high-level cascaded H-bridge multi-level inverters.

• Asian Journal of Innovation and Policy
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• v.11 no.3
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• pp.397-420
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• 2022

This research was conducted by applying a bibliometric analysis to determine the dynamics of research topics from ten percent of research output (international publications) generated by Indonesian scientists from the period of 1945-2021. This study utilizes VOSviewers version 1.6.18 for analysis and visualization of bibliometric networks. The research results indicate that 50.24% of Indonesian international publications are published in the form of articles, with subjects such as: Agricultural and Biological Sciences, Medicine, and Earth and Planetary Sciences as the most dominating subject areas. Regarding the author, Tjia, MO from Bandung Institute of Technology was acknowledged as the top author in terms of the number of publications produced for two periods. The article entitled "Global, regional, and national prevalence of overweight and obesity in children and adults during 1980-2013: A systematic analysis for the Global Burden of Disease Study 2013" (Ng et al., 2014) became the most cited one.