• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.727-731
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• 2005

Design and manufacturing process of a full color LED microdislay fabricated by standard CMOS technology and containing an array of aluminum / nanostructured porous silicon reverse biased light emitting Schottky diodes will be discussed. Being of a solid state construction, this microdisplays are cost-effective, thin and light in weight due to very simple device architecture. Its benefits include also super high resolution, wide viewing angles, fast response time and wide operating temperature range. The advantages of full integration of an LED-array and driving circuitry onto a Si-chip will be also discussed.

• Journal of the Optical Society of Korea
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• v.12 no.2
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• pp.79-87
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• 2008

We have developed a miniature fisheye lens with $190^{\circ}$ field of view operating simultaneously in the visible and the near infrared wavelengths. The modulation transfer function characteristic for the visible wavelength is sufficient for a mega-pixel-grade image sensor. The lens also has a fair resolution in the infrared wavelength region. The calibrated $f-{\theta}$ distortion is less than 5%, and the relative illumination is over 90%. In consequence, a sharp wide-angle image can be obtained which is uniform in brightness over the entire range of field angles. The real image heights for the visible and the near infrared wavelengths have been fitted to polynomial functions of incidence angle with sub-pixel accuracies. Combined with the near equidistance projection scheme of the lens, this lens can be advantageously employed in various image-processing applications requiring a wide-angle lens.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1050-1054
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• 2001

Relatively high rotating speed propulsion shafting system of the large Ro-Ro Ferry has a greate risk of the resonance of the many wide local panels as well as the high frequency global vibratory modes. Therefore, from the initial design stage, it is necessary to control the vibration characteristics of the wide panels with detail so as not to be resonant with the blade number order excitation due to the propellers in the normal operating speed range. The procedure of the vibration analysis and the structural redesign for prevention of vibration is introduced.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.56.4-57
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• 2015

We present the optical design and a sensitivity analysis for a wide field of view (FOV) instrument operating at UV and IR wavelengths. The ongoing investigation is performed in collaboration with Omnisys Instruments (Sweden) and focuses on a telluric-limb-viewing instrument that will fly in a low Earth orbit to study mesospheric wave structures over a wide range of horizontal scales in the altitude range 80 - 100 km. The instrument has six wavelength channels which consist of 4 channels of IR and 2 of UV. We are proposing an optical design based on three mirror aplanatic off-axis reflective system. The entrance pupil diameter and effective focal length are 45 mm and 270 mm, respectively. The FOV is $5.5^{\circ}{\times}1^{\circ}$ and the secondary mirror is set for stop. The optical specification is required to have an encircled energy of at least 80 % within a diameter of 21 um. We performed sensitivity analysis for the longest wavelength of 772 nm in consideration of the diffraction limit of system. The results show that tolerance limits for positions and angles of the mirrors are not very sensitive compared with typical error budgets of manufacturing and assembling process. The secondary mirror has the most sensitive tolerance for surface figure of 250 nm in root-mean-square.

• Journal of Power Electronics
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• v.9 no.5
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• pp.736-747
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• 2009

A new type of single-phase Z-source AC/AC converter based on a single-phase matrix converter is proposed in this paper. The proposed single-phase Z-source AC/AC converter has unique features; namely that the output voltage can be bucked and in-phase/out-of-phase with the input voltage; that the output voltage can be boosted and in-phase/out-of-phase with the input voltage. The converter employs a safe-commutation strategy to conduct along a continuous current path, which results in the elimination of voltage spikes on switches without the need for a snubber circuit. The operating principles of the proposed single-phase Z-source AC/AC converter are described, and a circuit analysis is provided. To verify the performance of the proposed converter, a laboratory prototype based on a TMS320F2812 DSP was constructed. The simulation and the experimental results verified that the output voltage can be bucked-boosted and in-phase with the input voltage, and that the output voltage can be bucked-boosted and out-of-phase with the input voltage.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.11
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• pp.57-62
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• 1998

In this paper, tunable transconductor shows good linearity over a wide input voltage range are proposed. The proposed transconductor employ operating in the nonsaturation(ie., linear) region to improve circuit simplicity and tunability and 6.8V$\_$p-p/ wide input range. Also the circuit employ source-coupled differential pair to provide true differential input and can achieve both positive and negative transconductance values. The proposed circuits are implemented using a 1.2 $\mu\textrm{m}$ single poly double metal n-well CMOS technology. The THD characteristic of proposed circuit is less than 1% for a differential input voltage of up to 6V$\^$p-p/ when supply bias condition is V$\_$DD/=-V$\_$ss/=5V, I$\_$B/=20, 40${\mu}$A, and frequency of input signal is 1KHz.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.25-26
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• 2015

Inductive Power Transfer (IPT) method becomes more and more popular for the Electric Vehicle (EV) battery charger due to its convenience and safety in comparison with plugged-in charger. In recent years, Lithium batteries are increasingly used in EVs and Constant Current/Constant Voltage (CC/CV) charge needs to be adopted for the high efficiency charge. However, it is not easy to design the IPT Battery Charger which can charge the battery with CC/CV charge under the wide range of load variation due to the wide range of variation in its operating frequency. This paper propose a new design and control method which makes it possible to implement the CC/CV mode charge with minimum frequency variation (less than 1kHz) during all over the charge process. A 6.6kW prototype charge has been implemented and 96.1% efficiency was achieved with 20cm air gap between the coils.

• ETRI Journal
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• v.42 no.4
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• pp.505-517
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• 2020

The increasing size and complexity of deep neural networks (DNNs) necessitate the development of efficient high-performance accelerators. An efficient memory structure and operating scheme provide an intuitive solution for high-performance accelerators along with dataflow control. Furthermore, the processing of various neural networks (NNs) requires a flexible memory architecture, programmable control scheme, and automated optimizations. We first propose an efficient architecture with flexibility while operating at a high frequency despite the large memory and PE-array sizes. We then improve the efficiency and usability of our architecture by automating the optimization algorithm. The experimental results show that the architecture increases the data reuse; a diagonal write path improves the performance by 1.44× on average across a wide range of NNs. The automated optimizations significantly enhance the performance from 3.8× to 14.79× and further provide usability. Therefore, automating the optimization as well as designing an efficient architecture is critical to realizing high-performance DNN accelerators.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.1
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• pp.44-52
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• 2017

This paper describes a 100 kW high-efficiency isolated DC-DC converter for DC distribution system. The DC-DC converter consists of two dual-active-bridge (DAB) converters in parallel. The operating principle of the DAB converter is explained, and the algorithm for parallel operation of the DAB converters is proposed. Simulation and experiments are conducted to verify the performance of the proposed system. Experimental results demonstrate that the developed converter excellently marks 97.4 percent of peak efficiency under its normal operating condition.

• Journal of Power System Engineering
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• v.8 no.3
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• pp.5-10
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• 2004

This work deals with a controlled auto-ignition (CAI) single cylinder gasoline engine, focusing on the extension of operating conditions. In order to keep a homogeneous air-fuel mixing, the fuel injector is water-cooled by a specially designed coolant passage. Investigated are the engine emission characteristics under the wide range of operating conditions such as 40 in the air-fuel ratio, 1000 to 1800 rpm in the engine speed, $150\;to\;180^{\circ}C$ in the inlet-air temperature, and $80^{\circ}$ BTDC to $20^{\circ}$ ATDC in the injection timing. A controlled auto-ignition gasoline engine which has the ultra lean-burn with self-ignition of gasoline fuel can be achieved by heating inlet air. It can be achieved that the emission concentrations of carbon monoxide, hydrocarbons and nitrogen oxides had been significantly reduced by CAI combustion compared with conventional spark ignition engine.