• KSBB Journal
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• v.22 no.6
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• pp.438-442
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• 2007

A biosensor using electrochemically-active bacteria (EAB) enriched in three-electrode electrochemical cell, was developed for the determination of biochemical oxygen demand (BOD) in wastewater. In the electrochemical cell, the positively poised working electrode with applying a potential of 0.7 V was used as an electron acceptor for the EAB. The experimental results using artificial and raw wastewater showed that the current pattern generated by the biosensor and its Coulombic yield were proportional to the concentration of organic matter in wastewater. The correlation coefficients of BOD vs Coulombic yield and $BOD_5$ vs Coulombic yield were 0.99 and 0.98, respectively. These results indicate that the biosensor enriched with the EAB capable of transferring electrons directly toward the electrode can be utilized as a water-quality monitoring system due to a quick and accurate response.

• Korean Chemical Engineering Research
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• v.45 no.3
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• pp.242-248
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• 2007

For an optimal design of automotive electric system, it is important to have a reliable modeling tool to predict the charge-discharge behaviors of the automotive battery. In this work, a two-dimensional modeling was carried out to predict the charge-discharge behaviors of a 12-V automotive lead-acid battery. The model accounted for electrochemical kinetics and ionic mass transfer in a battery cell. In order to validate the modeling, modeling results were compared with the experimental data of the charge-discharge behaviors of a lead-acid battery. The discharge behaviors were measured with three different discharge rates of C/5, C/10, and C/20 at operating temperature of $25^{\circ}C$. The batteries were charged with constant current of 30A until the charging voltage reached to a predetermined value of 14.24 V and then the charging voltage was kept constant. The discharge and charge curves from the measurements and modeling were in good agreement. Based on the modeling, the distributions of the electrical potentials of the solid and solution phases, the porosity of the electrodes, and the current density within the electrodes as well as the acid concentration can be predicted as a function of charge and discharge time.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.1795-1801
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• 2009

In this study, a portable flashlight which can manually generate the electricity by using sunlight was developed so that it can be used in the extreme environmental condition such as no-electricity condition. Battery is charged by using solar battery during the day, but when sunlight is not avalible during the night or rainy day, a handle is rotated to generate the electricity in order to charge the battery manually. To improve the brightness of the light, light is concentrated by using the optical lens. Low electric consumption circuit is used for the longer operating time by suppress electrical consumption while lamp is discharged. A circuit is designed and used for steady electrical curris dand voltage to insure steady battery charging. Super-discharge circuit and protection circuit are used for the super discharge of battery when it is not used for a long time. Also the constant charge is possible by using houseware adapter. As a result, a portable flashlight is designed to charge with sunlight during day, and with houseware adapter during night. A portable flashlight is also designed to irradiate longer distances by improvement of the brightness of the light using the optical lens. Thus, it forms white natural ray of light making possible for night reading.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1459-1467
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• 2011

This paper proposes the effective method to improve the protection from induced lightning Surge by making common grounding from individual grounding. Common grounding under equipotential principle is more effective than individual grounding for lightning Surge protection, and so common grounding is indicated as international technical standard under the AC power supply system with neutral line. So, this paper is to propose the effective way of induced lightning Surge protection method for currently installed power supply system which has no neutral grounded line and individual grounding which are weak for lightning Surge protection. This proposal can improve the power supply system as has neutral line, and improve the grounding system to common grounding system. And also this paper proposes to make effective equipotential system with voltage variable shunting devices for lightning Surge protection.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.292_293
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• 2009

현재 산업발달로 인한 전력수요 증가와 IT산업의 혁신적인 발달로 고장으로 인한 정전 발생시 사회생활에 미치는 영향이 커지게 되었다. 위성도시의 발달로 인한 지중선로는 필연적으로 증가하고 있으며 지중선로의 특이 환경은 점검 및 유지보수등의 고정밀도를 요한다. 장거리 지중선로의 문제점으로 초고압케이블에 대한 가시적인 또는 주기적인 점검으로 설비상태를 파악하기에는 한계가 존재할 수밖에 없다. 이에 본 논문은 인력순시에 한계를 극복하고 무선통신장비 등을 이용하여 지중선로내 과학화 장비를 이용한 상시감시 체계를 소개하고자 한다.

• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.21-26
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• 2016

The ESD(electrostatic discharge) protection performance of PPS(PMOS pass structure) embedded N-type silicon controlled rectifier(NSCR_PPS) device with different implant of channel blocking region was discussed for high voltage I/O applications. A conventional NSCR standard device shows low on-resistance, low snapback holding voltage and low thermal breakdown voltage, which may cause latch-up problem during normal operation. However, our proposed NSCR_PPS devices with modified channel blocking structure demonstrate the improved ESD protection performance as a function of channel implant variation. Therefore, the channel blocking implant was a important parameter. Since the modified device with CPS_PDr+HNF structure satisfied the design window, we confirmed the applicable possibility as a ESD protection device for high voltage operating microchips.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.603-605
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• 2005

전력수요의 증대에 따른 계동모의 확장에 따라 관련기기는 초고압 및 대용량화 추세에 있다. 이러한 관련기기들 중에서도 특히 154/22.9kV 전력용 변압기는 고장시 수용가의 정전범위가 방대하고 변압기 내부 고장의 복구비용 또한 막대하므로 경제적 손실은 물론 사회적 영향도 크다. 우리나라에서는 1980년 초기부터 154/22.9kV 전력용 변압기의 고장이 급증하였으며, 이러한 원인은 주로 직전접지 방식을 채택하고 있는 한전 계통에서 배전선의 지락고장에 의한 지락고장 전류가 변압기 중성점을 통하여 변압기에 충격을 가함으로써 변압기 권선 단락 절연파괴 및 ULTC 고장 등이 발생하는 것으로 밝혀졌다. 따라서 한전에서는 변압기 중성점으로 흐르는 지락고장전류의 저감을 위해 변압기 중성점 접지 리액터(NGR: Neutral Ground Reactor)를 설치하여 운전하고 있으며, 결과 변압기 고장이 크게 감소하였다. 그러나 모선 절체시 변압기 1, 2차측 차단기 Trip 고장이 발생하였으며, 고장 발생 원인은 NGR 보호계전기 59GT 계전기의 오동작에 의한 86T Lock Out 계전기 동자으로 변압기 1, 2차측 차단기 Trip 고장이 발생한 것으로 추정된다. 따라서 본 논문에서는 무부하 모선 차단시 59GT 계전기에 나타나는 이상 전압을 EMTP (electro-magnetic transient program)를 이용하여 분석하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.215-218
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• 2013

This paper proposes the effective method to improve the protection from induced lightning surge by making common grounding from individual grounding. Common grounding under equipotential principle is more effective than individual grounding for lightning surge protection, and so common grounding is indicated as international technical standard under the AC power supply system with neutral line. So, this paper is to propose the effective way of induced lightning surge protection method for currently installed power supply system which has no neutral grounded line and individual grounding which are weak for lightning surge protection. This proposal can improve the power supply system as has neutral line, and improve the grounding system to common grounding system. And also this paper proposes to make effective equipotential system with voltage variable shunting devices for lightning surge protection.

• Journal of Sensor Science and Technology
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• v.24 no.3
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• pp.208-213
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• 2015

The purpose of this study is to optimize the design of a capacitive pressure sensor element using the simulation of electrical characteristics. The simulation of the ceramic sensor diaphragm ($Al_2O_3$) was performed by permitting pressure to change the curvature of the diaphragm. The pressure capacitance ($C_P$) was increased from 19.63 pF to 15.26 pF by applying pressure because the distance between the electrodes has been changed from $30{\mu}m$ to $15{\mu}m$. When the thickness of the diaphragm was changed to 0.46~0.52 mm, a larger capacitance change showed in accordance with the reduced thickness, which means an increase of sensitivity. However, considering the viewpoint of the signal linearity, it was selected for the optimum thickness of the diaphragm to 0.50 mm. The designed sensor element based on simulated results was tested to measure the output characteristics. Comparing of simulated and measured results, there was a margin of error of approximately 2%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.96-100
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• 2001

We have measured the space charge distribution and PD patterns simultaneously in XLPE under AC voltages by modified PEA method in order to investigate the effect of space charge on PD patterns in XLPE with air-gap. From the experimental results, we found that the dynamic space charge accumulated on the surface of XLPE due to the PD dominantly affects the PD pattern in the dielectric-barrier structure and governs the voltage across the air-gap. Moreover, the space charge formed by applying DC voltage still remained after applying AC voltage, which means that the space charge formed during DC strength test is likely to be fatal to the long-time AC insulating characteristics of HV equipments. On the other hand, the PD patterns was much influenced by the pre-formed space charge by DC application. Therefore, it is possible to detect the effects of space charge by monitoring the infinitesimal change of PD patterns before and after DC strength.