• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.397-400
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• 2001

This paper proposed a speed adaptive control system with load torque observer and feed-forward compensation using neural network for air compressor system driven an induction motor. The motor receive impact load change under the influence of piston movement of up and down, and so it difficult to obtain good speed control characteristics. With real-time adjusting control gain estimated in neural network, control characteristics of motor is improved. The validity of the proposed system is confirmed through the theoretical analysis and computer simulation.

• ETRI Journal
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• v.26 no.5
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• pp.486-492
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• 2004

The emergence of wide channel bandwidth wireless standards requires the use of a highly linear, wideband integrated CMOS baseband chain with moderate power consumption. In this paper, we present the design of highly linear, wideband active RC filters and a digitally programmable variable gain amplifier. To achieve a high unity gain bandwidth product with moderate power consumption, the feed-forward compensation technique is applied for the design of wideband active RC filters. Measured results from a $0.5{\mu}m$ CMOS prototype baseband chain show a cutoff frequency of 10 MHz, a variable gain range of 33 dB, an in-band IIP3 of 13 dBV, and an input referred noise of 114 ${\mu}Vrms$ while dissipating 20 mW from a 3 V supply.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.3
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• pp.319-325
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• 2015

This paper presents an efficient vibration energy harvester with a piezoelectric (PE) cantilever. The proposed PE energy harvester increases the efficiency through minimization of hardware complexity and hence reduction of power dissipation of the circuit. Two key features of the proposed energy harvester are (i) incorporation synchronized switches with a simple control circuit, and (ii) a feed-forward buck converter with a simple control circuit. The chip was fabricated in $0.18{\mu}m$ CMOS processing technology, and the measured results indicate that the proposed rectifier achieves the efficiency of 77%. The core area of the chip is 0.2 mm2.

• Annual Conference on Human and Language Technology
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• 2015.10a
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• pp.124-128
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• 2015

문맥의존 철자오류는 해당 단어만 봤을 때에는 오류가 아니지만 문맥상으로는 오류인 문제를 말한다. 이러한 문제를 해결하기 위해서는 문맥정보를 보아야 하지만, 형태소 분석 단계에서는 자세한 문맥 정보를 보기 어렵다. 본 논문에서는 형태소 분석 정보만을 이용한 철자오류 수정을 위한 문맥으로 사전훈련(pre-training)된 단어 표현(Word Embedding)를 사용하고, 기존의 기계학습 알고리즘보다 좋다고 알려진 딥 러닝(Deep Learning) 기술을 적용한 시스템을 제안한다. 실험결과, 기존의 기계학습 알고리즘인 Structural SVM보다 높은 F1-measure 91.61 ~ 98.05%의 성능을 보였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.11a
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• pp.3-6
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• 2006

멀티레벨의 feed-forward 네트워크에 대한 학습 방법은 기울기 방법과 전역 최적화방법으로 나눌 수 있다. 역전파 또는 그 변형적인 방법들과 같은 기울기 하강 방법은 편리하기 때문에 여러 분야에서 다양하게 사용되고 있다. 하지만, 역전파와 관련된 가장 큰 문제는 지역 최소점에 빠진다는 것이다. 따라서 본 논문에서 기울기 하강 방법의 단순성을 침범하지 않고 지역 최소점을 극복할 수 있는 개선된 기울기 하강 방법을 제안한다. 제안하는 방법은 상위 연결과 하위연결을 분리하여 훈련하고 평가하기 때문에 이원적인 기울기 하강 방법이라 칭한다. 그렇기 때문에, 은닉층 유닛의 목표 값들은 하위 연결의 평가 툴로써 사용한다. 논문에서 제안하는 방법의 성능은 다양한 실험을 통해서 검증된다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.12
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• pp.1737-1741
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• 2015

A multi-channel CMOS transimpedance amplifier(TIA) array is realized in a $0.18-{\mu}m$ CMOS technology for the applications of panoramic scan LADAR systems. Each channel consists of a PIN photodiode and a feed-forward TIA that exploits an inverter input stage followed by a feed-forward common-source amplifier so as to achieve lower noise and higher gain than a conventional voltage-mode inverter TIA. Measured results demonstrate that each channel achieves $76-dB{\Omega}$ transimpedance gain, 720-MHz bandwidth, and -20.5-dBm sensitivity for $10^{-9}$ BER. Also, a single channel dissipates the power dissipation of 30 mW from a single 1.8-V supply, and shows less than -33-dB crosstalk between adjacent channels.

• Journal of Power Electronics
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• v.19 no.4
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• pp.1011-1019
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• 2019

In this paper, a buck-flyback (fly-buck) stand-alone photovoltaic (PV) system for charge balancing with a differential power processor (DPP) circuit is proposed. Conventional feed-back DPP converters draw differential feed-back power from the output of a string converter. Therefore, the power is always through the switches and diodes of the string converter. Because of the returning conduction path, there are always power losses due to the resistance of the switch and the forward voltage of the diode. Meanwhile, the proposed feed-back DPP converter draws power from the magnetically-coupled inductor in a string converter. This shortens the power path of the DPP converter, which reduces the power losses. In addition, the extra winding in the magnetically-coupled inductor works as a charge balancer for battery-stacked stand-alone PV systems. The proposed system, which uses a single magnetically-coupled inductor, can control each of the PV modules independently to track the maximum power point. Thus, it can overcome the power loss due to the power path. It can also achieve charge balancing for each of the battery modules. The proposed topology is analyzed and verified using 120W hardware experiments.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.729-737
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• 2009

This paper introduces the machine tools feed system, which can be optimized the control's performance through simulation and the adjustment of the mechanical components. One method simulates the frequency response of the speed-loop with the design value using the MATLAB application, so that all of the interpolation axis can be equal to the response bandwidth, resulting in a high accuracy rate. The other method sees the mechanical component being adjusted by analyzing the results of various experiments. Lastly, this client's program is able to change the parameters that are related to the FFD, as well as the parameters in the friction compensation of the OPEN-CNC.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.379-382
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• 2006

The flow forming has been used to produce long thin walled tube parts, with reduced forming force and enhanced mechanical and surface quality for a good finished part, compared with other method formed parts. Especially, the flow forming is suitable for making high precision thin walled cylinders, such as rocket motor cases, combustion chamber, hydraulic cylinders and high-pressure vessels and so on. In this paper, finite element analysis of three-roller forward and backward flow forming for combustion chamber is carried out to study efforts of forming depth and feed rate on forming force. The axial and radial forming forces of forward flow forming on several forming depth and feed rate conditions are compared with those of backward flow forming.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.4
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• pp.357-361
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• 2018

Forward osmosis (FO) process has been attracting attention for its potential applications such as industrial wastewater treatment, wastewater reclamation and seawater desalination. Particularly, in terms of fouling reversibility and operating energy consumption, the FO process is assumed to be preferable to the reverse osmosis (RO) process. Despite these advantages, there is a difficulty in the empirical step due to the lack of separation and recovery techniques of the draw solution. Therefore, rather than using FO alone, recent developments of the FO process have adapted a hybrid system without draw solution separation/recovery systems, such as the FO-RO osmotic dilution system. In this study, we investigated the performance of the hollow fiber FO module according to various operating conditions. The change of permeate flow rate according to the flow rates of the draw and feed solutions in the process operation is a factor that increases the permeate flow rate, one of the performance factors in the positive osmosis process. Our results reveal that flow rates of draw and feed solutions affect the membrane performance, such as the water flux and the reverse solute flux. Moreover, use of hydraulic pressure on the feed side was shown to yield slightly higher flux than the case without applied pressure. Thus, optimizing the operating conditions is important in the hollow fiber FO system.