• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.4
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• pp.38-45
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• 2002

This paper describes the technical issues of the domestic standard and guideline for lightning protection systems in order to propose the countermeasures in damage of computer and electronic equipments due to lightning surges. The relationship between the current flow in the down conductor and the current flow in the steel conduit surrounding the down conductor was investigated as a function of the installation method of down conductors. Also the experiments were conducted to evaluate the influences of the skin effect on the down conductor systems. As a result, when the down conductor were bonded to the steel conduit, the down conductor and the steel conduit act as one conductor, so much mure lightning current flows in the steel conduit than in the copper down conductor because of the skin effect and choking effect. Therefore to reduce the adverse effects such as the electrostatic induction and side flashes caused by the potential rise of down conductors due to lightning currents, it is extremely effective to bond the down conductor to the steel conduit and steel frame of structures.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.1
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• pp.71-78
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• 2002

This paper is concerned with the design and implementation of magnetic damper system to reduce the vibration of suspension system actively. Cylindrical type electro-magnetic actuator with permanent magnet is analyzed and effective controller design is made. Magnetic force analyzed and transfer function for the total system is determined by experimental data using error minimization method. For experiments, simple suspension structure system is utilized, in which a magnetic damper composed of permanent magnet and digital controller is attached. In order to drive the system, bipolar power amplifier of voltage control type is utilized. Stable and high speed control board is used to perform digital control logic for the given system. This paper shows that the magnetic damper system using phase-lead controller excellently reduces vibration of 1-D.O.F (degree of freedom) suspension system.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.12
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• pp.50-59
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• 2000

This paper presents a new SRAM testing method for various faults by monitoring dynamic power supply currents. The peak value of Iddt pulses when the transition write operation is performed, is prominently different from that of a fault free case. Using the observation, a new memory test algorithm is developed which consists of only write operations. The new test algorithm using dynamic power supply current testing, has length of 7n, where n is the number of cells in SRAMs. Compared to the previous March B algorithm, the test length has been reduced by 7/17, and can detect additional hard-to-detect faults.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.2
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• pp.195-200
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• 2011

A low power Hall thruster is under development for orbit maintenance of a small Earth observing satellite. Both cylindrical and annular type thrusters were manufactured and tested to characterize the performance of cylindrical Hall thrusters. Results were described through comparative analyses. Cylindrical thrusters were manufactured in two different channel diameter dimensions, 28 mm and 50 mm. Thrust, ion velocity and ion current were measured in various operating conditions. The results show that cylindrical thrusters are more efficient in mass utilization and voltage utilization, but less efficient in current utilization than annular one.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.1
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• pp.56-64
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• 2007

Recently, the high frequency link boost DC/DC converter has been used widely for PCS (Power Conditioning System) because of the requirements of small size and low cost. However, the high frequency link boost DC/DC converters applied the conventional voltage-fed converter and current-fed converter have some problems like high conduction losses and high surge voltage due to high circulating current and leakage inductance, respectively. To improve these problems, a novel secondary LLC (called SLLC) series resonant converter is proposed in this paper and its theoretical analysis, its operating waveforms, simulation and experimental results for a boost DC/DC converter using SLLC series resonant topology verifies the proposed topology. 800W experimental prototype is tested.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.132-139
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• 2004

Unsymmetrical faults are classified into single line-to-ground faults, line-to-line faults, or double line-to-ground faults in receiving and distribution power systems. Many of overhead distribution-line faults are single line-to-ground faults, and lightning surge arresters are stressed by system frequency overvoltages due to unsymmetrical faults. In this work, the unsymmetrical faults in receiving and distribution systems were experimentally simulated, and the characteristics of total leakage current flowing through lightning surge arresters due to various unsymmetrical faults were investigated. As a result, a little variations of the leakage current flowing through Zinc oxide (ZnO) surge arresters in the range of $\pm$10[%] voltage regulations were observed. It could be concluded that the unsymmetrical faults have no effect on the long-term life performance of ZnO surge arresters in effective grounding systems. On the other hand, the magnitude of the leakage current flowing through ZnO surge arrester elements under single line-to-ground faults was more than 140 times as compared with that under normal operating voltages in ineffective grounding systems. But abnormal voltages caused by line-to-line faults and double line-to-ground faults have a little effect on total leakage current of ZnO surge arrester elements.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.8
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• pp.1-12
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• 2001

The adaptive learning circuit is designed on the basis of modeling of MFSFET (Metal-Ferroelectric-Semiconductor FET) and the numerical results are analyzed. The output frequency of the adaptive learning circuit is inversely proportional to the source-drain resistance of MFSFET and the capacitance of the circuit. The saturated drain current with input pulse number is analogous to the ferroelectric polarization reversal. It indicates that the ferroelectric polarization plays an important role in the drain current control of MFSFET. The output frequency modulation of the adaptive learning circuit is investigated by analyzing the source-drain resistance of MFSFET as functions of input pulse numbers in the adaptive learning circuit and the dimensionality factor of the ferroelectric thin film. From the results, the frequency modulation characteristic of the adaptive learning circuit are confirmed. In other words, adaptive learning characteristics which means a gradual frequency change of output pulse with the progress of input pulse are confirmed. Consequently it is shown that our circuit can be used effectively in the neuron synapses of nueral networks.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.97-97
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• 2010

최근 자동차에서 경량화의 방안으로써 높은 강성을 요구하는 고장력강 사용이 증대 되고 있다. 그러나 고장력강은 저항 점용접 시 일반 강에 비해 높은 전류를 요구하며 계면파단 및 expulsion 발생이 용이하기 때문에 가용 전류 구간이 좁은 특성을 가진다. 많은 연구자들이 hold time, tempering 등의 process를 이용하여 고장력강의 저항 점용접성을 개선하고자 하였으나 생산 공정라인에 적용하기는 어려운 실정이다. 본 연구에서는 용접 공정 변수의 변화에 따른 용접성과 전극 형상 변화을 통한 고장력강 점 용접성 향상에 대한 연구를 실시 하였다. 고장력강의 점 용접성 비교하기 위해 표준 전극(S1)과 인위적으로 가공한 전극(M1)을 사용하였으며, 실험에 사용된 판재는 두께 1.4mm의 DP590이며, 그 결과 표준전극(S1) 보다 가공 전극(M1)의 가용 전류 구간이 0.5kA 정도 넓은 것으로 확인 되었다. 두 전극을 사용한 점용접 시험편들의 인장전단강도를 비교 해보면 표준전극(S1)을 적용한 점용접 시 인장전단강도는 KS B 0850 기준에 만족하나 계면 파단이 발생 하였다. 가공 전극(M1)을 적용한 점용접 시 인장전단강도는 규격 기준에 만족하나 버튼 파단이 발생 하였다. 두 전극을 적용한 점용접부 형상 및 용접부 온도 분포에대해 저항점용접 시뮬레이션 프로그램(SORPAS)을 이용하여 실험 결과 값과 비교 분석하였고 파단모드의 변화에 대한 원인 분석을 도출 하였다.

• Analytical Science and Technology
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• v.7 no.4
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• pp.483-492
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• 1994

Direct solid analysis of various kinds of metal samples has been conducted by glow discharge. In this laboratory, the gas-jet assisted glow discharge(GJGD) device has been developed and characterized. The effect of changes in applied current, cell pressure and flow rate on atomic emission signals obtained from a jet-assisted cathodic sputtering was investigate. The emission intensities of Cu, Zn, and Ar were measured. They were increased with the current. But the intensities were decreased by increasing the flow rate of argon due to the diffusion and transportation of particles into plasma. By increasing the pressure of the cell, the intensities were greatly decreased because of enhancement of redeposition onto the surface of the sample.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.269-275
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• 2005

This article describes the development on a new style active hybrid bearing system including both merits of an aerostatic bearing system and a magnetic bearing system. The developed active hybrid bearing system has several advantages: exact rotation, robust controller against the variation of a disturbance, improvement of stiffness and a damper of the system at a high-speed operation, and constraints of the heat generated by a bias current. In order to measure a rotating error due to the change of a cutting force and the variation of a system parameter, a CCS (Cylindrical Capacity displacement Sensor) was used.