• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03a
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• pp.7-7
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• 2010

Energy harvesting from the environment has been of great interest as a standalone power source of wireless sensor nodes for Ubiquitous Sensor Networks(USN). In particular, the piezoelectric energy harvesting from ambient vibration sources has intensively researched because it has a relatively high power density comparing with other energy scavenging methods. Through recent advances in low power consumption RF transmitters and sensors, it is possible to adopt a micro-power energy harvesting system realized by MEMS technology for the system-on-chip. However, the MEMS energy harvesting system has some drawbacks such as a high natural frequency over 300 Hz and a small power generation due to a small dimension. To overcome these limitations, we devised a novel power generator with a spiral spring structure as shown in the figure. The natural frequency of a cantilever could be decreased to the usable frequency region (under 300 Hz) because the natural frequency depends on the length of a cantilever. In this study, the natural frequency of the energy harvester was a lower than a normal cantilever structure and sufficiently controllable in 50 - 200 Hz frequency region as adjusting weight of a proof mass. Moreover, the MEMS energy harvester had a high energy conversion efficiency using a shear mode ($d_{15}$) is much larger than a 33 mode ($d_{33}$) and the energy conversion efficiency is proportional to the piezoelectric constant (d). We expect the spiral type MEMS power generator would be a good candidate for a standalone power generator for USN.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.21-24
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• 2008

Proton Exchange Membrane Fuel Cell (PEMFC) is an attractive candidate for residential power generator due to fast start-up and stop, high efficiency, low emission, and high power density. In this study, we employ short module stack to understand the performance of the unit cell of the stack in terms of operating temperatures. To simulate the practical fuel cell stack of residential power generator, the structure and active area of the short module stack is kept the same as that of the practical fuel cell. The results shows that the electric potential of short module stack is different from the number of cells times the potential of unit cell because of cell-to-cell variation.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.7
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• pp.356-363
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• 2001

A SRG (Switched Reluctance Generator) has many advantages such as high efficiency, low cost, high-speed capability and robustness compared with other of machine. But the control methods that have been adopted for SRGs are complicated. This paper proposes a simple control method using the PID controller which only controls turn-off angles while keeping turn-on angles of SRG constant. In order to keep the output voltage constant, the turn-off angle for load variations is controlled by using linearity between the generated current and turn-off angle since the reference generated current can be led through the voltage errors between the reference and the actual voltage. The suggested control method enhances the robustness of this system and simplifies the hardware and software by using only the voltage and the speed sensors. The proposed method is verified by experiments.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.717-718
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• 2008

We developed the protection program for the generator fault protection system and each module of the digital protective relay H/W for loading the protection program. The protective algorithm for the generator is 51, 51G/N, 46P/N, 47P/N, 50G/N, and 32, and we developed each fault protection program. And we must design high efficiency microprocessor, CT, and PT for realtime measuring, relaying and high accuracy of measurement, also. From now on digital protective relay must be operated with integrated management systems. For this point, we must load various industrial protocol on the digital protective relay. In this research, we developed each protective relay H/W module according to above conditions. And we designed real-time operating system in order that each protective algorithm is operated with realtime processing on the H/W system.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.357-359
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• 2005

In this paper, a new SEPIC-Flyback converter with a single transformer has been proposed, which is suitable for a fuel cell based power generation system. The proposed converter is superposition of sepic and flyback converter mode. It has outstanding high boosting output voltage, component utilization and high efficiency characteristics under the inherently severe low output voltage of the fuel cell generator. The proposed converter for a full cell generator is described and verified by simulation and experimental result that make used of the Polymer Electrolyte Membrane Fuel Cell(PEMFC) Generator.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.05b
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• pp.14-18
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• 2003

This paper presents the pipeline architecture for the low and column address generator of 2D DCT/IDCT(Discrete Cosine Transform/Inverse Discrete Cosine Transform). For the real time process of image data, it is required that high speed operation and small size hardware In the proposed architecture, the area of hardware is reduced by using the DA(distributed arithmetic) method and applying the concepts of pipeline on the parallel architecture. As a results, the designed pipeline of the low and column address generator for 2D DCT/IDCT architecture is implemented with an efficiency and high speed compared as the non-pipeline architecture. And the operation speed is improved about 50％ up. The design for the proposed pipeline architecture of DCT/IDCT is coded using VHDL.

• Journal of the Korean Society of Visualization
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• v.21 no.3
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• pp.85-92
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• 2023

In this study, we present experimental results of cavitating flow around a vortex generator which is used to improve the flow in the wake of ships and enhance propulsion efficiency. We conducted experiments at the CNU cavitation tunnel on a total of six vortex generators, two different aspect ratios and three taper ratios. We recorded cavity patterns using a high-speed camera and quantitatively evaluated cavity fraction using OpenCV. The most important finding of this study is that the vortex cavity generated at a root leading edge of the vortex generator develops at a specific angle.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.291-293
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• 2003

A semiconductor switch-based fast hi-polar high voltage pulse generator is proposed in this paper The proposed pulse system is made of a thyristor based-rectifier, DC link capacitor, a push-pull resonant inverter, a high voltage transformer. secondary capacitor, a high voltage IGBT & diode stacks, and a variable capacitor. The proposed system makes hi-polar high voltage sinusoidal waveform using resonance between leakage inductance of the transformer and secondary capacitor and transfers energy to output load at maximum of the secondary capacitor voltage. Compared to previous hi-polar high voltage pulse power supply using nonlinear transmission line, the proposed pulse power system using only semiconductor switches has simple structure and gives high efficiency

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.184-187
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• 1990

This paper presents the self-matched line pulse generator and the concerned principles on its operation and characteristics are mentioned. The circuit consists of a charged transmission line and a high speed switch, and it generates a square wave pulse with the very fast rise time. The generated waveform depends on the load resistance. As the load resistance is infinite, a single rectangular wave pulse is generated and its efficiency is nearly unity.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.423-426
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• 1999

This paper describes a driving scheme of the series hybrid electric vehicle that we have developed. Both series HEV and parallel HEV are well known. We chose series HEV because it provides good energy efficiency in urban driving and operates in all-electric mode in performance. And engine-Generator is driven at constant speed with constant load to maintain the low emission. And the battery supplies power during high-load and receive energy during low-load