• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.6 s.360
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• pp.50-59
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• 2007

[ $0.18-{\mu}m$ ] CMOS 1.2-V 2nd-order ${\Sigma}{\Delta}$ modulator with full-feedforward topology is designed. Using full-feedforward topology makes op-amp performance requirements much less stringent, therefore it has been adopted as a good candidate for low-voltage low-power applications throughout the world. Also, ${\Sigma}{\Delta}$ modulator is designed with top-down design approach, therefore various nonideal effects of op-amp are modeled in this paper.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1470-1471
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• 2008

We present a front-side micromachined thermopile with high sensitivity in the 3-5${\mu}m$ window, and discuss its application to a novel non-dispersive infrared (NDIR) $CO_2$ gas sensor with a light source emitting collimated light. The micromachined thermopile shows a measured sensitivity of 30 mV/W and a $D^*$ of $0.3{\times}10^8cm^{\surd}Hz/W$. Using this newly fabricated thermopile, we also have successfully developed a small, sensitive NDIR $CO_2$ detector module for accurate air quality monitoring systems in energy-saving building and automotive applications. The novel sample cavity comprising specular reflectors around the light bulb is configured to uniformly emit collimated light into the entrance aperture of the cavity in order to enhance the sensitivity of NDIR $CO_2$ detector.

• Environmental Engineering Research
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• v.24 no.3
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• pp.456-462
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• 2019

Hydrocarbon contamination is among the most challenging problems in soil remediation. Electrokinetic method can be a promising method to remediate hydrocarbon-contaminated soils. Electrokinetic method consists of different transport phenomena including electro-migration, electrophoresis, and electroosmotic flow. Electroosmotic flow is the main transport phenomenon for hydrocarbon removal in soil porous media. However, the main component of hydrocarbons is the hydrophobic organic which indicates low water solubility; therefore, it makes the electroosmotic flow less effective. The objective of the present study is to enhance electrokinetic remediation of diesel-contaminated silty sand by increasing the solubility of the hydrocarbons in the soil and then increase the efficiency. For this purpose, sodium dodecyl sulfate (SDS) was used as a catholyte. In this content, SDS 0.05 M was used as catholyte and $Na_2SO_4$ 0.1 M was used as an anolyte. Low (1 V/cm) and high (2 V/cm) voltage gradients were used in periodic and continuous forms. The best removal efficiency was observed for high voltage gradient (2 V/cm) in a periodic form, which was 63.86. This result showed that a combination of periodic voltage application in addition to the employment of SDS is an effective method for hydrocarbon removal from low permeable sand.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.7
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• pp.1191-1198
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• 2001

MMIC low noise amplifiers for millimeter-wave application using 0.15 $\mu$m pHEMT have been presented in this paper. The design emphasis is on active device model and EM simulation. The deficiency of conventional device models is identified. A distributed device model has been adapted to circumvent the scaling problems and, thus, to predict small signal and noise parameters accurately. Two single-ended low noise amplifier are designed using distributed active device model for Q-band(40 ∼ 44 GHz) and V-band(58 ∼65 GHz) application. The Q-band amplifier achieved a average noise figure of 2.2 dB with 18.3 dB average gain. The V-band amplifier achieved a average noise figure of 2.9 dB with 14.7 dB average gain. The design technique and model employed provides good agreement between measured and predicted results. Compared with the published data, this work also represents state-of-the-art performance in terms of gain and noise figure.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.620-626
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• 1988

GaAs solar cells may be the most attractive and efficient power source of a satellite. GaAs is more radiation tolerant and less temperature sensitive than widely used silicon. $Al_{x}$ Ga$_{1-x}$ As/GaAs solar cells have been designed and fabricated by Liquid Phase Epitaxial method. GaAs solar cells, of which structure is about 0.2 .mu.m p$^{+}$ - window layer, 0.6-1.O .mu.m Ge-doped p-layer. 3.mu.m n-GaAs layer and n$^{+}$ - buffer layer, have been characterized as a function of operating temperature from 25 .deg.C to 130 .deg.C. Open circuit voltage decreases linearly with increasing temperature by 1.4-1.51 mV/ .deg.C while degradation of silicon solar cells is about 2.2-2.5 mV/ .deg.C, short circuit current does not increase much with increasing temperature. Relative efficiency decreases with increasing of temperature by about 0.21-0.29 %/ .deg.C. Efficiency degradation of silicon solar cells with temperature is known to be about 0.5%/ .deg.C and our results show GaAs solar cells may be an excellent candidate for concentrated solar cells.ells.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.464-466
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• 2003

우리나라는 1980년대 이후 급격한 경제성장에 따라 년 10%대의 급격한 전력수요 증가를 보이고 있으며, 1인당 전력소비량 또한 매년 큰 폭의 증가세를 보이고 있다. 특히, 주요한 전력 수요 증가지대가 경인 지역에 집중되어 있으나, 이 지역은 인구 밀집지역으로 환경과 입지적인 관점에서 새로운 발전원을 개발하기가 곤란하다. 이에 따라 대용량 발전단이 있는 중서부권이나 영동권으로부터 수요지인 경인지역으로의 대규모 전력전송로가 필요하게 되었다. 이에 따라 1979년부터 765kV로의 전압격상을 준비하였으며, 1983년부터 765kV 연구개발을 시작하여 1997년 10월에 1차로 765kV 송전선로에 345kV 가압을 시작하여 2002년 5월 8일에 역사적인 765kV 송전을 개시하였다. 전력계통운용에서 765kV 송전선로의 중요도가 매우 커지게 됨으로써 국내 최초로 적용되는 765kV송전선로 보호시스템의 정동작 유무를 정확히 판단하여 전력계통의 보호 신뢰도를 향상시키는 문제가 중요하게 대두 되었다. 본 논문에서는 시각동기장치가 부착된 보호계전기 시험장치를 이용하여 양단 변전소에서 동시에 EMTP와 RTDS 둥으로 검토된 송전선로 고장상태를 인가하여 보호시스템의 정동작 여부를 종합적으로 판정하는 시험 기술을 개발하여 실적용한 사례와 향후 사용 계획에 대해서 기술하였다.

• Journal of Power Electronics
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• v.16 no.3
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• pp.1209-1217
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• 2016

This paper presents a novel charge pump scheme that combines the advantages of Fibonacci and Dickson charge pumps to obtain 30 V voltage for display driver integrated circuit application. This design only requires four external capacitors, which is suitable for a small-package application, such as smart card displays. High-amplitude (<6.6 V) clocks are produced to enhance the gate drive of a Dickson charge pump and improve the system's current drivability by using a voltage-doubler charge pump with a pulse skip regulator. This regulation engages many middle-voltage devices, and approximately 30% of chip size is saved. Further optimization of flying capacitors tends to decrease the total chip size by 2.1%. A precise and simple model for a one-stage Fibonacci charge pump with current load is also proposed for further efficiency optimization. In a practical design, its voltage error is within 0.12% for 1 mA of current load, and it maintains a 2.83% error even for 10 mA of current load. This charge pump is fabricated through a 0.11 μm 1.5 V/6 V/32 V process, and two regulators, namely, a pulse skip one and a linear one, are operated to maintain the output of the charge pump at 30 V. The performances of the two regulators in terms of ripple, efficiency, line regulation, and load regulation are investigated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.4
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• pp.1059-1067
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• 1996

A 128/129 dual-modulus prescalar IC is designed for application to frequency synthesizers in high frequency communication systems. The FET logic used in this design is SCFL(Source Coupled FET Logic), employing depletion-mode 1.mu.m gate length GaAs MESFETs with the threshold voltage of -1.5V. This circuit consists of 8 flip-flops, 3 OR gates, 2 NOR gates, a modulus control buffer and I/O buffers, which are integrated with about 440 GaAs MESFETs on dimensions of 1.8mm. For $V_{DD}$ and $V_{SS}$ power supply voltages 5V and -3.3V Commonly used in TTL and ECL circuits are determined, respectively. The simulation results taking into account the threshold voltage variation of .+-.0.2V and the power supply variation of .+-.1V demonstrate that the designed prescalar can operate up to 2GHz. This prescalar is fabricated using the ETRI MMIC foundary process and the measured maximum operating frquency is 621MHz.

• Journal of Biosystems Engineering
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• v.32 no.4
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• pp.230-236
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• 2007

In this study, a tail rotor system for an agricultural RF controlled helicopter was developed and tested. This study concluded the mechanical development of the 'Agro-heli' by completing the tail rotor system and its radio console. The RF control system was closely related with the tail system for the control of flying attitude. The thrust of the tail system balance off the reaction torque, created by the main rotor. Lifting tests with and without the tail system were compared for estimating the consumption of power. The tail system would use $4{\sim}5%$ of the total power which was in an acceptable range. Flying performance and attitude was visually inspected. It showed reliable and safe control during the distance flying trials and could be adapted for utilization in aerial applications. Aerial application using an RF controlled agricultural helicopter may make precise and timely spraying possible.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3400-3404
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• 2011

A new rhodamine B-coumarin conjugate (1) capable of recognizing both $Cu^{2+}$ and $Fe^{3+}$ using two different detection modes have been designed and synthesized. The metal ion induced optical changes of 1 were investigated in $CH_3CN-H_2O$ (1:1, v/v, HEPES 50 mM, pH = 7.0) solution. Sensor 1 exhibits selective colorimetric recognition of $Cu^{2+}$ and fluorescent recognition of $Fe^{3+}$ with UV-vis and fluorescence spectroscopy, respectively. Moreover, both of the $Cu^{2+}$ and $Fe^{3+}$ recognition processes are observed to be barely interfered by other coexisting metal ions.