• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.5
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• pp.1094-1107
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• 2013

NTRU cryptosystem has been suggested for protecting wireless body area networks, which is secure in the sense of traditional cryptanalysis. In this paper, we fulfill the first power analysis attack on the ultra-low-power environment of wireless body area networks. Specifically, two practical differential power analyses on NTRU algorithm are proposed, which can attack the existing countermeasures of NTRU. Accordingly, we suggest three countermeasures against our attacks. Meanwhile, practical experiments show that although the attacks in this paper are efficient, our countermeasures can resist them effectively.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.06a
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• pp.143-144
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• 2017

다양한 응용 매체의 유비쿼터스(ubiquitous) 연결을 위한 사물 인터넷 (Internet-of-Thing; IoT) 시스템은 저전력 광역 통신 (Low Power Wide Area; LPWA) 기술을 기반으로 한다. 저전력 광역 통신 시스템의 충족조건인 전송 거리 확대와 낮은 전력 사용은 시스템 전력 운용 관점에서는 상호 충돌하는 조건이다. 이를 위해 신호대역폭을 줄여 수신기 감도 (receiver sensitivity) 를 개선하는 초협대역 (Ultra Narrow Band; UNB) 기술이 주목받고 있다. 여기서는 이러한 저전력 광역 통신을 위한 초협대역 변조 기술의 신호 대 잡음 비(Signal-to-Noise Ratio; SNR)에 대해 분석한다.

• Journal of Power Electronics
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• v.16 no.3
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• pp.960-969
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• 2016

High-power three-level voltage-source converters are widely utilized in high-performance AC drive systems. In several ultra-power instances, the harmonics on the grid side should be reduced through multiple rectifications. A combined harmonic elimination method that includes a dual primary-side series-connected winding transformer and selective harmonic elimination pulse-width modulation is proposed to eliminate low-order current harmonics on the primary and secondary sides of transformers. Through an analysis of the harmonic influence caused by dead time and DC magnetic bias, a synthetic compensation control strategy is presented to minimize the grid-side harmonics in the dual primary side series-connected winding transformer application. Both simulation and experimental results demonstrate that the proposed control strategy can significantly reduce the converter input current harmonics and eliminates the DC magnetic bias in the transformer.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.107-119
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• 2021

The cross-flow turbine is one of the most famous and widely used hydraulic power systems for a long time. The cross-flow turbine is especially popular in many countries and remote regions where off-grided because of its many benefits such as low cost, high efficiency at low head, simple structure, and easy maintenance. However, most modern turbines, including the cross-flow turbine, are unsuitable for the ultra-low head situation, known as less than 3m water head or zero head with over 0.5m/s flow velocity. In this study, we demonstrated a 20kW class inverted-type cross-flow turbine's performance. First, we reevaluated our previous studies and introduced how to design the inverted-type cross-flow turbine. Secondly, we fabricated the 20kW class inverted-type cross-flow turbine for the performance test. And then, we designed a testbed and installed the turbine system in the demonstration facility. In the end, we compare the demonstration with its previous CFD results. The comparing result shows that both CFD and real model fitted on guide vane angle at 10 degrees. At the demonstration, we achieved 42% turbine efficiency at runner speed 125 RPM.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.37-38
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• 2013

This paper presents an intuitive and powerful way to study and design motor drive control. The control of induction motors, as most widely used machines, is discussed. Thanks to ultra low latency and high fidelity Hardware-in-the-Loop systems, different aspects of up-to-date drive regulation are examined. A power stage, comprised of a grid voltage source, a rectifier, a VSC inverter and an induction motor, is emulated on the HIL platform in real time. A digital signal controller is plugged into the interface board and connected to the HIL emulation platform, without any hardware modifications. For motor control and power electronics applications, a dedicated Texas Instruments TMS320F2808 DSP is chosen. The same controller can drive an emulation platform and a real device with no modifications. Current and speed control loop test results are presented and discussed.

• The Journal of the Convergence on Culture Technology
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• v.6 no.3
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• pp.361-367
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• 2020

This paper proposes the battery-less ultra-low-power self-powered cooperating artificial neural networks device for embedded and IoT systems. This device can work without extraneous power supplying and can cooperate with other neuromorphic devices to build large-scale neural networks. This device has energy harvesting modules, so that can build a self-powered system and be used everywhere without space constraints for power supplying.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.1
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• pp.30-39
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• 2017

Interests in fuel cell based power generation systems are on the steady rise owing to various advantages such as high efficiency, ultra low emission, and potential to achieve a very high efficiency by a synergistic combination with conventional heat engines. In this study, the performance of a hybrid system which combined a molten carbonate fuel cell (MCFC) and an indirectly fired micro gas turbine adopting carbon dioxide capture technologies was predicted. Commercialized 2.5 MW class MCFC system was used as the based system so that the result of this study could reflect practicality. Three types of ambient pressure hybrid systems were devised: one adopting post-combustion capture and two adopting oxy-combustion capture. One of the oxy-combustion based system is configured as a semi-closed type, while the other is an open cycle type. The post-combustion based system exhibited higher net power output and efficiency than the oxy-combustion based systems. However, the semi-closed system using oxy-combustion has the advantage of capturing almost all carbon dioxide.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.6
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• pp.241-249
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• 2012

In the many countries, research about ultra wideband wireless transmission technique is widely studied for efficient utilization of frequency resource due to a sudden increase of demand of frequency resource all over the world. The ultra wideband communication system has the some specific advantages. First, it can transmit data with high speed, second short transmission range can increase the frequency reuse rate, and finally it has high security property. However, there is a interference between ultra wideband system and other communication system but study to solve this problem is insufficient. To efficient utilization of limited frequency resource, a novel frequency avoidance technique and setup the standardization of frequency interference must need. So, the purpose of this paper is that increases communication efficiency of microwave communication systems to analyze the technical trends for transmission of the low power device, and to research the implementation and technical research of wireless access network technique of wideband communication systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.12
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• pp.2136-2139
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• 2008

Chaotic oscillators can generate wide-band signals and the spectrum characteristics of the wide-band signals are not changed by switching on and off the output power of the oscillators. When communication systems use a chaotic oscillator, the communication system need not a local oscillator and a mixer used in conventional transceivers. Therefore the configuration of a communication system using a chaotic oscillator is simple and have the characteristics of low-power consumption. In this paper we design and implement a chaotic oscillator. And the test results of the implemented chaotic oscillator for UWB systems are presented. The implemented chaotic oscillator has -8.11dBm of the output power with 500MHz channel bandwidth at 3.4GHz of the center frequency and has about 410MHz of -10dB bandwidth.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.4
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• pp.595-606
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• 2022

Korea has the characteristics of traditional power system such as large-scale power generation and large-scale power transmission systems, including 20 GW large-scale power generation complexes in several regions with unit generator capacity exceeding 1.4 GW, 2-3 ultra-high-voltage transmission lines that transport power from large-scale power generation complexes, and 6 ultra-high-voltage transmission lines that transport power from non-metropolitan areas to the metropolitan area. Due to the characteristics of the power system, the penetration level for renewable energy is low, but due to frequency stability issue, some generators are reducing the output of generators. In the future, the issue of maintaining the stability of the power system is expected to emerge as the most important issue in accordance with the policy of expanding renewable energy. When non-inertial inverter-based renewable energy, such as solar and wind power, surges rapidly, the means to improve the power system stability in an independent system is to install a natural inertial resource synchronous condenser (SC) and a virtual inertial resource BESS in the system. In this study, we analyzed the effect of renewable energy on power system stability and the BESS effect to maintain the minimum frequency through a power system simulation. It was confirmed that the BESS effect according to the power generation constraint capacity reached a maximum of 122.81 %.