• The Journal of Information Systems
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• v.27 no.3
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• pp.141-160
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• 2018

Purpose The purpose of this study is to verify mobile game users' perceived utilities about real (price) and virtual (Ruby) currencies, which are the major factors of in-app purchase (IAP) widely used as a business model in a mobile game industry. Design/methodology/approach By using sales volume and sales frequency data for products sold in an 'S' mobile game from the 'D' mobile game company, we conducted a conjoint analysis according to the procedure recommended by Bicheno (2009). Findings The results of this study indicate that (1) mobile game users have greater utility for a virtual currency (Ruby) than for a real currency (price), (2) mobile game users' utility for virtual (Ruby) and real (price) currencies varies depending on sales volume and sales frequency, as well as (3) mobile markets (e.g., Google Play Store vs. Apple App Store), and (4) mobile game users have greater utility for a virtual currency (Ruby) which can be used readily than later.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.233-235
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• 2001

This paper deals with frequency control of demand users that have power plants by under-frequency relay. The demand users supply electrical power to a part of their loads by their power plants and to other rest of their loads by utility. While electrical power supply is stopped by faults of utility network, the system of demand users network is separated from total power system and their system frequency goes below normal limits. In this paper, this situation and the effect of under-frequency relay application are simulated by EMTDC.

• 전자공학회논문지 IE
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• v.43 no.2
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• pp.63-69
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• 2006

Islanding phenomenon of utility-connected PV power conditioning systems(PV PCS) can cause a variety of problems and must be prevented. If the real and reactive powers supplied by PV PCS are closely matched to those of load, islanding detection by passive methods becomes difficult. The active frequency drift(AFD) method, called the frequency bias method, enables islanding detection by forcing the frequency of the voltage in the islanding to drift up or down. In this paper, non-detection zone(NDZ) of AFD is analyzed for the islanding detection method of utility-connected PV PCS by simulation tool PSIM.

• Asian Journal of Innovation and Policy
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• v.10 no.2
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• pp.236-248
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• 2021

The objective of this study is to introduce the urban utility concept that combines urban growth and urban disasters in the aspect of a conceptual theory. While many studies focused on the dollar amount damaged from a disaster, it requires adding not just building damages or human body losses but also the quality of life satisfaction. An issue in measuring the quality of life satisfaction needs to introduce a proper mode quantifying it. This study introduces the urban utility change in measuring the negative impacts of a disaster on urban life, which has been rarely investigated. To identify urban utility, urban flooding that is a cross-sectoral agenda and important to both developed and developing countries was adopted to respond to its increased frequency and damages, encouraging governments to focus on flood control policies. By combining a literature review on urban utility and urban growth, this study defined the urban utility concept as a net benefit of a resident with earnings subtracting housing and commuting costs. The theoretical study also explained that urban utility and its components dynamically change as per urban growth and disasters that even reversely affect urban growth. Because the urban utility can be one of the useful indices to appreciate the relationship between a disaster and urban growth, it is highly expected to apply for similar disaster impacts on urban areas, including COVID-19 and various global warming issues.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.548-553
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• 2003

The frequency and phase angle of the utility voltage are important in many industrial systems. this paper present a detailed analysis of single-phase digital PLL control for utility connected systems. and its performance under utility conditions with noise is discussed. The experimental results demonstrate phase tracking capability in the single-phase grid-connected operation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.3
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• pp.479-484
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• 2018

This paper describes domestic technical standard of Photovoltaic(PV) PCS(Power Conditioning Systems)-Characteristics of the utility interface. This standard tests utility compatibility and personnel safety and equipment protection of PV inverter performance functions. Especially utility compatibility part includes test items of 1)voltage, current and frequency, 2)normal voltage operating range, 3)DC injection, 4)normal frequency operating range, 5)harmonics and 6)waveform distortion, 7)power factor of PV inverter. Therefore in this paper each test item of domestic technical standard is studied and analyzed and finally full tested by PV inverter performance function.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.1
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• pp.60-68
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• 2010

Recently, Power Conditioning System (PCS) tends to require more compact, higher efficiency and power density with better performance. A novel topology consisted of LLC resonant inverter and Low Frequency (LF) cyclo-converter for connecting to utility line is able to meet these requirements. The technical operating analysis is described and 1kW prototype is tested and verified the performances through connecting the 110Vac 60Hz utility line. Efficient results are described.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1281-1283
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• 2001

An investigation into power conditioners that interface with photovoltaic array and utilities has been completed. The rating for this investigation is residential system(3-5kW) that interface with a 220V single phase utility connection. As the result of this investigation, a 3kW high frequency PWM IGBT inverter feeding a high frequency isolation transformer with a sinusoidal current wave was selected. The output of the transformer rectified with a diode bridge rectifier four IGBT, used as 60Hz switched, reverse the polarity of the rectified current on every other half cycle of the utility voltage. Even though the high frequency link system used more power semiconductors a net size, weight, and parts cost saying result compared to the other systems due to elimination of 60Hz transformer.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.467-469
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• 2001

An investigation into power conditioners that interface with photovoltaic array and utilities has been completed. The rating for this investigation is residential system(3-5kW) that interface with a 220V single phase utility connection. As the result of this investigation, a 3kW high frequency PWM IGBT inverter feeding a high frequency isolation transformer with a sinusoidal current wave was selected. The output of the transformer rectified with a diode bridge rectifier, four IGBT, used as 60Hz switched, reverse the polarity of the rectified current on every other half cycle of the utility voltage. Even though the high frequency link system used more power semiconductors, a net size, weight, and parts cost saving result compared to the other systems due to elimination of 60Hz transformer.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.46-49
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• 2001

An investigation into power conditioners that interface with photovoltaic array and utilities has been completed. The rating for this investigation is residential system(3-5kVA) that interface with a 220V single phase utility connection. As the result of this investigation, a 3kVA high frequency PWM IGBT inverter feeding a high frequency isolation transformer with a sinusoidal current wave was selected. The output of the transformer rectified with a diode bridge rectifier. four IGBT, used as 60Hz switched, reverse the polarity of the rectified current on every other half cycle of the utility voltage. Even though the high frequency link system used more power semiconductors, a net size, weight, and parts cost saving result compared to the other systems due to elimination of 60Hz transformer.