• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.669-672
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• 2002

Establishment of the Quantum Hall Resistance(QHR) Standard as national resistance standard using a room temperature DCC resistance bridge is described. A simple method are used to obtain the current dependence and error of 10: 1 ratio of the bridge instead of the method using a cryogenic resistance bridge. Measurement uncertainty of the system is estimated as $0.14{\times}10^{-6}$ and it is confirmed that the QHR standard is agreed well with the QHR of other NMIs using the cryogenic resistance bridge within the uncertainty, More improvement about performance of the QHR device and 10: 1 ratio accuracy is still under progress.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.3
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• pp.267-273
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• 2018

From the experiments of various temperature and gas compositions, total resistance which is composed of ohmic resistance, anode resistance, cathode resistance and Nernst loss was calculated wit simple assumption. In this work, the anode and the cathode resistance was modelled with new equation which can account for the correlation between the operating temperature and the gas composition. The proposed model can predict the resistance with maximum error of 2.57% and employed in the simulation of molten carbonate fuel cells.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.2
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• pp.149-159
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• 2017

In this study, the numerical investigation of ship motions and added resistance at constant forward velocity of KVLCC2 model is presented. Finite volume CFD code is used to calculate three dimensional, incompressible, unsteady RANS equations. Numerical computations show that reliable numerical results can be obtained in head waves. In the numerical analyses, body attached mesh method is used to simulate the ship motions. Free surface is simulated by using VOF method. The relationship between the turbulence viscosity and the velocities are obtained through the standard ${\kappa}-{\varepsilon}$ turbulence model. The numerical results are examined in terms of ship resistance, ship motions and added resistance. The validation studies are carried out by comparing the present results obtained for the KVLCC2 hull from the literature. It is shown that, ship resistance, pitch and heave motions in regular head waves can be estimated accurately, although, added resistance can be predicted with some error.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.10
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• pp.141-151
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• 1999

The resistance Spot Welding is widely used in the field of assembling the plates. However we don't still have any satisfactory solution, which is non-destructive quality evaluation in real-time or on-line, against it. Moreover, even though the rate of welding under the condition of expulsion has been high until now, quality control of welding against expulsion hasn't still been established. In this paper, it was proposed on the quality assurance technique of resistance spot welding pieces using Neuro-Fuzzy algorithm. Four parameters from electrode separation signal in the case of non-expulsion, and dynamic resistance patterns in the case of expulsion are selected as fuzzy input parameters. The parameters consist of Fuzzy Inference System are determined through Neuro-Learning algorithm. And then, fuzzy Inference System is constructed. It was confirmed that the fuzzy inference values of strength have within ${\pm}$4% error specimen in comparison with real strength for the total strength range, and the specimen percent having within ${\pm}$1% error was 88.8%. According to KS(Korean Industrial Standard), tensile-shear strength limit for electric coated of zinc is 400kgf/mm2. Judging to the quality of welding is good or bad, according to this criterion and the results of inference, the probability of misjudgement that good quality is valuated into poor one was 0.43%, on contrary it was 2.59%. Finally, the proposed Neuro-Fuzzy Inference System can infer the tensile-shear strength of resistance spot welding pieces with high performance for all cases-non-expulsion and expulsion. And On-Line Welding Quality Inspection System will be realized sooner or later.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2002.11a
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• pp.307-312
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• 2002

For accuracy of an experiment, measure changing of grounding resistance by short period after construction and investigated the efficiency of grounding's different methode of parallel connection. We could confirm on measurement's accuracy, error through comparing the theoretical value and measured value. Therefore, reduction ratio can be expected from execution measurement to receive a target resistance value. By the result, we could evaluate the method of rod grounding electrode's proper execution

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.55-57
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• 2005

In this study, modeling of the CD stud welding system was conducted considering mechanical and electrical components. The electrical components such as arc resistance, cable resistance, capacitance, internal resistance and cable inductance were found to affect the output waveform significantly. The calculated results showed food agreements with the experiment results within 20% error. The main defect of CD stud welding with 1010 steel stud and SS400 steel plate was the void trapped between stud and base metal. The effect of the spring force and stud tip size on void formation was investigated.

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.143-145
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• 2003

The purpose of research is to measure power and dynamic resistance value through RMS module. Specially designed RMS-DC hardware module was tested. Its output which is obtained every half cycle was compared with that of commercial weld checker. The results show good agreement and the relative error in the measurement was found to be around 5%.

• Journal of the Korean Society of Safety
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• v.9 no.4
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• pp.42-48
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• 1994

A rotor flux error-based approach for correcting the rotor time constant estimation used in the slip frequency calculator of indirect field oriented controller is presented in this paper. The controller was derived from the d-q induction machine model. Slip frequency gain is dependent on the machine parameter errors. And parameter errors result in rotor flux error. Thus, estimated rotor flux is compared to commanded rotor flux. The error between them is used for the estimation of rotor time constant. Simulation results which demonstrate the performance of this approach are presented.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.10
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• pp.555-561
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• 1999

This paper proposes a new compensation algorithm for stator resistance that is crucial for improving the direct vector control performance of an induction motor. This algorithm is based on the flux estimator that is derived from the stator voltage equation. Since a flux estimator is dependent on the stator resistance, a flux error originates from the variation of the stator resistance. This parameter mismatch in the estimator thereafter affects the flux and torque response. Accordingly, a new compensator has been designed to offset this degradation in the responses. The proposed compensator is very simple to implement and does not require any modifications to the motor model or any special interruptions of the controller. The value of the stator resistance is attained in real time through measuring the terminal voltage and current. The effectiveness of the proposed scheme has been confirmed through both simulation and experimentation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.2
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• pp.97-104
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• 2001

The effects of the position of potential probe on the measurements of the ground resistance in the fa11-of-potential method are described. The ground resistance is theoretically calculated by applying the 61.8[%] rule, and then the potential probe is located on the straight line between the grounding electrode to be measured and the current probe. However, sometimes the grounding electrode to be measured and the measuring potential and current probes in on-site test might not be arranged on the straight line with adequate distance because there are building, roadblock construction and other establishments. Provided that the grounding electrode to be measured and the measuring potential probes are out of position on the straight line, the measurement of the ground resistance classically falls into an error and the measured ground resistance should be corrected. In this work, measurements were focused on the grounding electrode system made by the ground rods of 2.4 m long. The measuring error was increased with increasing the angle which is made by the 3-points of the grounding electrode to be measured, the potential anti current probes, and it was a negative. That is, all of the measured ground resistances ware less than the true ground resistance.