• 한국전기전자재료학회논문지
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• 제20권10호
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• pp.912-917
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• 2007

Many electrochemical power devices such as solid state batteries and solid oxide fuel cell have been studied and developed for solving energy and environmental problems. An amperometric gas sensor usually generates sensing signal of electric current along the proportion of the concentration of target gas under the condition of limiting current. For narrow variations of gas concentration, the amperometric gas sensor can show higher precision than a potentiometric gas sensor does. In additional, cross sensitivities to interfering gases can possibly be mitigated by choosing applied voltage and electrode materials properly. In order to improve the sensitivity to $NO_2$, the device was attached with Au reference electrode to form the amperometric gas sensor device with three electrodes. With the fixed bias voltage being applied between the sensing and counter electrodes, the current between the sensing and reference electrodes was measured as a sensing signal. The response to $NO_2$ gas was obviously enhanced and suppressed with a positive bias, respectively, while the reverse current occurred with a negative bias. The way to enhance the sensitivity of $NO_2$ gas sensor was thus realized. It was shown that the response to $NO_2$ gas could be enhanced sensitivity by changing the bias voltage.

• 전기학회논문지
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• 제64권9호
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• pp.1315-1322
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• 2015

This paper proposes an active islanding detection method for the BESS (Battery Energy Storage System) with 3-phase inverter which is connected to the AC grid. The proposed method adopts the DDSRF (Decoupled Double Synchronous Reference Frame) PLL (Phase Locked-Loop) so that the independent control of positive-sequence and negative-sequence current is successfully carried out using the detected phase angle information. The islanding state can be detected by sensing the variation of negative-sequence voltage at the PCC (Point of Common Connection) due to the injection of 2-3% negative-sequence current from the BESS. The proposed method provides a secure and rapid detection under the variation of negative-sequence voltage due to the sag and swell. The feasibility of proposed method was verified by computer simulations with PSCAD/EMTDC and experimental analyses with 5kW hardware prototype for the benchmark circuit of islanding detection suggested by IEEE 1547 and UL1741. The proposed method would be applicable for the secure detection of islanding state in the grid-tied Microgrid.

• 유공압시스템학회논문집
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• 제4권3호
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• pp.13-21
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• 2007

A forklift is a motive machine powered by LPG, diesel engine or electric motors. The internal combustion engine type forklift is equipped with automatic transmission to meet the required drive load as well as the easy operation of the vehicle. This paper deals with the shift control and endurance test controller which is developed for the functional test of the newly designed automatic transmission on a dynamometer test bench. Its major function is to control the proportional solenoid currents, which is directly related to clutch pressures, for the given reference current trajectory during shift and sequential operation of shift schedule designed for the durability test at each gear. It also has the ability to monitor all the necessary test data through RS232 communication and log them to disk files. The current controller of embedded system is designed from the identified dynamics of solenoid coil and the current reference can be easily modified with a user interface software on PC so as to match the shift data by experiments.

• Corrosion Science and Technology
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• 제7권4호
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• pp.197-200
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• 2008

In this paper, physical scale modeling was employed to identify the configurations of ICCP system and the electric field signatures. Computational boundary element modeling technique has been used to simulate the performance of the CP system and to predict the associated electric fields signatures. The optimization methods combined with the computer models and physical scale modeling will be presented here, which enable the optimum system design to be achieved both in terms of the location and current output of the anode but also in the location of reference electrodes for impressed current cathodic protection(ICCP) systems. The combined methodology was utilized to determine optimal placement of ICCP components (anodes and reference electrodes) and to evaluate performance of ICCP system for the 2%, 10% and 14% wetted hull coatings loss. The objective is to design the system to minimise the electric field while at the same time provide adequate protection for the ship. The results show that experimental scale modeling and computational modeling techniques can be used in concert to design an optimum ICCP system and to provide information for quickly analysis of the system and its surrounding environment.

• 한국전기전자재료학회논문지
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• 제20권6호
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• pp.555-560
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• 2007

This paper describes the results of a study on the sealing integrity of polymer housed surge arrester based on the thermal mechanical test. The polymer housed surge arrester employs silicone insulating materials for its housing, instead of the conventional porcelain housing. The polymer housed surge arresters exhibited the highest sealing integrity because it is not air volume between the FRP(fiber reinforced plastics) module and the silicone housing. In accordance, the sealing integrity of station class surge arresters is investigated with moisture ingress test. And, the influence of sealing integrity was evaluated through such as measurement of the deflection, reference voltage, leakage current. In electrical characteristics, reference voltage decreased in the range of $16.45{\sim}16.15\;kV$ with after thermal mechanical test. In contrary, despite the continued moisture ingress, the polymer housed surge arresters exhibited almost the same leakage current value and the resistive leakage current has risen slightly. As a results, It was thought that the polymer housed surge arresters shows good stability with sealing integrity.

• 한국비블리아학회지
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• 제21권2호
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• pp.81-96
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• 2010

본 연구에서는 이용자 인식조사를 기반으로 하여 온라인 참고정보원용 메타데이터 항목을 제안하고 있다. 설문을 통해 4 관종의 사서들에게 17개 메타데이터 각각의 항목에 대한 필요성에 대해서 물었다. 또한 지난 2년 동안 운영되어온 시스템에의 메타데이터 입력현황과 이용자 인식조사 결과를 비교하였다. 이용자 인식조사와 시스템 입력비율을 기반으로, 17개의 메타데이터 항목 중 정보원 제목, 설명, 주제분야, 출판사, 유형, 식별자, 언어, 범위, 소장위치, 태그 항목은 반드시 포함되어야 할 항목으로 최종적으로 제안할 수 있었다. 또한 제작자와 저작권의 데이터가 실제 시스템에 입력된 비율은 각각 20.20%, 18.30%였으나, 설문응답자들은 각각 82.15%, 82.77%로 이 항목이 필요하다고 응답하였다. 따라서 이 두 개의 항목도 포함시키는 것이 적합하다고 본다. 다만, 시스템에의 입력비율이 3% 이하였던 형태, 원정보원, 날짜, 관련정보원, 기여자 항목에 대해 설문응답자의 거의 70% 이상이 이 모든 항목이 필요하다고 응답하였으므로 이에 대해서는 추가적인 연구가 진행되어야 한다고 본다.

• Journal of information and communication convergence engineering
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• 제10권2호
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• pp.187-193
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• 2012

A 1 GHz CMOS fast-lock phase-locked loop (PLL) is proposed to support the quick wake-up time of mobile consumer electronic devices. The proposed fast-lock PLL consists of a conventional charge-pump PLL, a frequency-to-digital converter (FDC) to measure the frequency of the input reference clock, and a digital-to-analog converter (DAC) to generate the initial control voltage of a voltage-controlled oscillator (VCO). The initial control voltage of the VCO is driven toward a reference voltage that is determined by the frequency of the input reference clock in the initial mode. For the speedy measurement of the frequency of the reference clock, an FDC with a parallel architecture is proposed, and its architecture is similar to that of a flash analog-to-digital converter. In addition, the frequency-to-voltage converter used in the FDC is designed simply by utilizing current integrators. The circuits for the proposed fast-lock scheme are disabled in the normal operation mode except in the initial mode to reduce the power consumption. The proposed PLL was fabricated by using a 0.18-${\mu}m$ 1-poly 6-metal complementary metal-oxide semiconductor (CMOS) process with a 1.8 V supply. This PLL multiplies the frequency of the reference clock by 10 and generates the four-phase clock. The simulation results show a reduction of up to 40% in the worstcase PLL lock time over the device operating conditions. The root-mean-square (rms) jitter of the proposed PLL was measured as 2.94 ps at 1 GHz. The area and power consumption of the implemented PLL are $400{\times}450{\mu}m^2$ and 6 mW, respectively.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.527-530
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• 2016

본 논문에서는 $0.35-{\mu}m$ standard CMOS 공정에서 낮은 전력을 소모하면서 낮은 전원전압에서 동작하는 곡률보상 기능을 갖는 기준전류/전압 발생 회로를 제안한다. 제안된 회로는 weak-inversion 영역에서 동작하는 MOS 트랜지스터들을 사용함으로써 1V 이하 전원전압에서 동작할 수 있다. 시뮬레이션 결과는 제안되는 곡률보상 기술을 사용하여 기존의 곡률보상 기능이 없는 BGR 회로들처럼 종 모양이 아닌 사인 곡선과 같은 모양을 나타내 작은 TC 값을 보여준다. 제안된 회로들은 모두 0.9V의 전원전압에서 동작한다. 먼저, 기준전압 발생 회로는 176nW 전력을 소모하며, 온도 계수는 $26.4ppm/^{\circ}C$이다. 기준전류 발생 회로는 194.3nW 전력을 소모하며, 온도 계수는 $13.3ppm/^{\circ}C$이다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(4)
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• pp.239-242
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• 2000

The color television signal and color receivers should be balanced for the same value of reference white to achieve colorimetric fidelity and to minimize interference. The NTSC signal is balanced for white at 6774 K and most existing receivers are balanced between 6500 K and 10000 K for many reasons. In this paper, we analyze beam current ratio, lightness, and channel gain ratio according to the color temperature for the three-tube projection HDTV. We also propose the brighter reference white for the three-tube projection HDTV based on the Helmholtz-Kohlrausch effect and the optical resolution of the image. In computer simulation we confirmed the most suitable reference white using the proposed analysis method.

• 한국문헌정보학회지
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• 제34권2호
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• pp.69-86
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• 2000

본 연구는 우리나라 대학도서관의 참고봉사 현황을 파악하고 그 개선방안을 모색하였다. 특히 본 연구는 '주제별 참고봉사'라는 개념을 도입하고, 이러한 개념을 현단계 우리나라 대학도서관에 적용할 수 있는 길을 찾아보았다. 이를 위해 본 연구는 전국 4년제 대학교 도서관의 참고사서를 대상으로 설문조사를 시행하였다. 본 연구의 결과는 우리나라 대학도서관의 현실적 여건에서 전문적인 서비스를 제공할 수 있는'주제전문사서'를 양성하는데 기초자료로 활용될 수 있을 것이다.