• Journal of Power Electronics
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• v.19 no.3
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• pp.665-675
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• 2019

Renewable energy based on photovoltaic systems is beginning to play an important role to supply power to remote areas all over the world. Owing to the lower output voltage of photovoltaic arrays, high gain DC-DC converters with a high efficiency are required in practice. This paper presents a novel interleaved DC-DC boost converter with a high voltage gain, where the input terminal is interlaced in parallel and the output terminal is staggered in series (IPOSB). The IPOSB configuration can reduce input current ripples because two inductors are interlaced in parallel. The double output capacitors are charged in staggered parallel and discharged in series for the load. Therefore, IPOSB can attain a high step-up conversion and a lower output voltage ripple. In addtion, the output voltage can be automatically divided by two capacitors, without the need for extra sharing control methods. At the same time, the voltage stress of the power devices is lowered. The inrush current problem of capacitors is restrained by the inductor when compared with high gain converters with a switching-capacitor structure. The working principle and steady-state characteristics of the converter are analyzed in detail. The correctness of the theoretical analysis is verified by experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.5
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• pp.499-508
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• 2002

In this paper, a novel wireless parallel operation algorithm of N+l redundant UPS system with no control interconnections for load-sharing is presented. The proposed control system eliminates the sensing noise and interconnections interference of conventional parallel operation system. To reduce a reactive power deviation in wireless control method, this technique automatically compensates for inverter parameter variation and line impedance imbalances with wireless auto-tuning method. In addition, to increase reliability on transient characteristics of parallel operation, a virtual injected impedance is adopted to eliminate a circulation current among inverter modules. Simulation results are provided in this paper to prove the proposed novel wireless algorithm.

• Journal of Communications and Networks
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• v.14 no.1
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• pp.51-62
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• 2012

The exponential growth in wireless services has resulted in an overly crowded spectrum. The current state of spectrum allocation indicates that most usable frequencies have already been occupied. This makes one pessimistic about the feasibility of integrating emerging wireless services such as large-scale sensor networks into the existing communication infrastructure. Cognitive radio is an emerging dynamic spectrum access technology that can be used for flexibly and efficiently achieving open spectrum sharing. Cognitive radio is an intelligent wireless communication system that is aware of its radio environment and that is capable of adapting its operation to statistical variations of the radio frequency. In ad hoc cognitive radio networks, a common control channel (CCC) is usually used for supporting transmission coordination and spectrum-related information exchange. Determining a CCC in distributed networks is a challenging research issue because the spectrum availability at each ad hoc node is quite different and dynamic due to the interference between and coexistence of primary users. In this paper, we propose a novel CCC selection protocol that is implemented in a distributed way according to the appearance patterns of primary systems and connectivity among nodes. The proposed protocol minimizes the possibility of CCC disruption by primary user activities and maximizes node connectivity when the control channel is set up. It also facilitates adaptive recovery of the control channel when the primary user is detected on that channel.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.285-288
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• 2012

Since the non-overlapping gate driver used in conventional DC-DC boost converters generates fixed dead-times, the converters suffer from the body-diode conduction loss or the charge-sharing loss. To reduce the efficiency degradation due to these losses, this paper presents a PWM DC-DC boost converter with adaptive dead-time control. In light loads, power switching is also employed to increase the efficiency. The designed DC-DC boost converter can thus achieve high efficiency at wide current range. The proposed DC-DC boost converter has 3.3V output from a 2.5V input with 0.18um technology. It operates at 500KHz and has a maximum power efficiency of 97.8%.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.6
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• pp.3411-3417
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• 2013

Over the last 10 years, the number of cancer survivors in South Korea has reached nearly one million with a survival rate of 49.4%. However, integrated supportive care for cancer survivors is lagging. One area in which the current cancer control policy needs updating is in the utilization of information and communication technology (ICT). The remarkable progress in the field of ICT over the past 10 years presents exciting new opportunities for health promotion. Recent communication innovations are conducive to the exchange of meta-information, giving rise to a new service area and transforming patients into active medical consumers. Consequently, such innovations encourage active participation in the mutual utilization and sharing of high-quality information. However, these benefits from new ICTs will almost certainly not be equally available to all, leading to so-called communication inequalities where cancer survivors from lower socioeconomic classes will likely have more limited access to the best means of making use of the health information. Therefore, most essentially, emphasis must be placed on helping cancer survivors and their caregivers utilize such advances in ICT to create a more efficient flow of health information, thereby reducing communication inequalities and expanding social support. Once we enhance access to health information and better manage the quality of information, as a matter of fact, we can expect an alleviation of the health inequalities faced by cancer survivors.

• Transactions on Semiconductor Engineering
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• v.2 no.2
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• pp.10-14
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• 2024

This paper presents a circuit design aimed at generating the required reference voltage and temperature sensor voltage in conjunction with an ADC, utilizing the current generated by temperature characteristics of BJT components for sensor data conversion. Additionally, two control methods are introduced to reduce the standard deviation of the circuit, resulting in over a ten-fold decrease in standard deviation. The proposed circuit occupies an area of 0.057mm² and was implemented using 55nm RF process.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.48-49
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• 2016

Interleaved 컨버터의 경우 전류 리플을 줄여 출력 필터의 사이즈를 줄이기 위해 많이 사용된다. 하지만 모듈간 소자값의 편차가 발생할 경우 전류 불평형을 초래하게 되며, 이는 리플저감효과를 감소시키거나 방열문제, 노화촉진, 그리고 오동작을 일으킬 가능성을 높이게 한다. 특히 공진형 컨버터의 경우 주파수 제어를 시도하기 때문에 Interleaving 기법을 적용하여 효용성을 얻기에는 제약이 많다. 본 논문에서는 이러한 소자값의 불일치로 인한 전류 불평형 문제를 해결하기 위해 위상천이변조 제어를 제안한다. 동작원리와 시스템에 대한 분석을 제시하고, 모의실험을 통해 타당성을 검증한다.

• Journal of Contemporary Eastern Asia
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• v.14 no.1
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• pp.23-43
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• 2015

In most of the world, the current trend in information technology is for open data movement that promotes transparency and equal access. An opposite trend is observed in China, which has the world's largest Internet population. The country has implemented sophisticated cyber-infrastructure and practices under the name of The Golden Shield Project (commonly referred to as the Great Firewall) to limit access to popular international web services and to filter traffic containing 'undesirable' political content. Increasingly, tech-savvy Chinese bypass this firewall and use Twitter to share knowledge on censorship circumvention and encryption to collectively troubleshoot firewall evasion methods, and even mobilize actions that border on activism. Using a mixed mythological approach, the current study addresses such networked knowledge sharing among citizens in a restricted web ecosystem. On the theoretical front, this study uses webometric approaches to understand change agents and positive deviant in the diffusion of censorship circumvention technology. On policy-level, the study provides insights for Internet regulators and digital rights groups to help best utilize communication networks of positive deviants to counter Internet control.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.34 no.1
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• pp.121-143
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• 2023

This study was conducted with the aim of identifying the current status of the national authority data construction project centered on the National Library of Korea for the effective construction and utilization of national knowledge information resources. It also aimed to reveal the possibility and improvement of the national information system with the international standard identification system, and suggesting future development plans. To this end, this study conducted interviews and questionnaires with members of the Korean National Authority Data Sharing System(KNASS). The survey consisted of items related to the current status and difficulties related to the authority, the use of the KNASS, the recognition and utilization of identifiers, the awareness and utilization of the linkage with ISNI, the Importance-Performance Analysis for activating the KNASS, and the overall satisfaction and improvement direction. As a result of the analysis, it was proposed to develop rules and guidelines related to the authority works, to increase the quantity and quality of authority data, to raise understanding of the importance and establish a efficient work system, to diversify the authority service and develop a utilization model, to link the KNASS with international identifiers, and to share the necessity of the KNASS.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.3
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• pp.107-116
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• 2005

The paper addresses modeling and analysis of a grid-connected photovoltaic generation system (PV system). PSCAD/EMTDC, an industry standard simulation tool for studying the transient behavior of electric power system and apparatus, is used to conduct all aspects of model implementation and to carry out extensive simulation study. This paper is aimed at sharing with the PSCAD/EMTDC user community our user-defined model for PV system applications, which is not yet available as a standard model within PSCAD/EMTDC. An equivalent circuit model of a solar cell has been used for modeling solar array. A series of parameters required for array modeling have been estimated from general specification data of a solar module. A PWM voltage source inverter (VSI) and its current control scheme have been implemented. A maximum power point tracking (MPPT) technique is employed for drawing the maximum available energy from the PV array. Comprehensive simulation results are presented to examine PV array behaviors and PV system control performance in response to irradiation changes. In addition, dynamic responses of PV array and system to network fault conditions are simulated and analysed.