• Journal of Korean Society for Atmospheric Environment
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• v.16 no.2
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• pp.113-120
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• 2000

Effects of sea-salts on the properties of aerosol collected in a coastal region were studied by applying a gas-particle equilibrium model SCAPE to the measurement data from Korea Cheju Island in summer 1994. It was found that the observed higher ammonium concentrations in fine particles (PM2.5) than in TSP were caused by forced evaporation of ammonium in coarse fraction of aerosol by sea-salts and the degree of evaporation was quantified through an application of SCAPE. By subtracting the sea-salt fraction from the measured concentra-tions the changes of aerosol property were also studied. The concentrations of nitrate at both TSP and PM2.5 decreased when alkaline sea-salt fraction was removed from the measured data. Estimates of aerosol acidity increased for most samples with sea salt loadings, However in some cases with high mass fractions of sea-salt components the aerosol acidity of PM2.5 decreased slightly. This is though to be related with the formation of solid salt with the removal of sea-salts.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.280-282
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• 1994

This paper proposes sliding mode state for robust speed control of induction motor. Sliding mode state observer is robust for measurement noise, modeling-error and load disturbance. The pole of sliding mode state observer can be placed at (0,0) in Z-plane for fast response. This method is, namely, deadbeat control. Sliding mode state observer output is discontinuous on a switching hyperplance, that causes harmful effects such as current harmonics and speed oscillation. In this paper, also the reducing method of the chattering of sliding mode state observer output is proposed. The proposed system is digitally implemented with TMS320C31.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.187-191
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• 1997

In this paper, we show that the rotor position of the bifilar-wound hybrid stepping motors for the closed-loop drives is detected by the phase current measurement. We propose an instantaneous phase current equation, which is the function of electrical angle, by the modeling of the stepping motor including motor driving circuits. We also analyze the relationship between phase current and rotor position from the computer simulation results. It is shown that the information about the rotor position is obtained from the phase current amplitude and its derivatives at the instance of ${\pi}/2$ electrical angle of excitation voltage.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.22-24
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• 1996

For two decades and more, a lot of research work on the biological effects of EMF(Electromagnetic Fields) on Human hearth have been reported. Power-frequency magnetic fields are a natural consequence of the flow of electricity. This paper deals with the modeling of electric utility facilities taking into account the line geometries. The magnetic fields profiles obtained from the computer simulation arc compared to those from measurements.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.6
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• pp.927-934
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• 2017

This paper is concerned with applicability of two-degree-of-freedom controllers to the recently suggested i-PID controllers, in which unknown parts of the plant are taken into account without any modeling procedure. First, i-PID controller with two-degree-of-freedom is applied to a specific model, called Anisochronic model, to confirm the usefulness of this method. Second, using the original examples of i-PID controllers, it is confirmed that performance/robustness of system are to be improved due to two-degree-of-freedom, especially when the input changes suddenly. It is seen that as the desired robustness increases the optimal value of two-degree-of-freedom parameter ${\alpha}_A$ would be negative. It is checked and verified that if this value was limited to 1 or less as is generally known, performance would be degraded.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.185-190
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• 2007

In this paper, minimum sampling rates and method of nonlinear characterization were suggested for low power, quasi-memoryless PAs. So far, the Nyquist rate of the input signal has been used for nonlinear PA modeling, and it is burdening Analog-to-digital converters for wideband signals. This paper shows that the input Nyquist rate sampling is not a necessary condition for successful modeling of quasi-memoryless PAs. Since this sampling requirement relives the bandwidth requirements for Analog-to-digital converters (ADCs) for feedback paths in digital pre-distortion systems, relatively low-cost ADcs can be used to identify nonlinear PAs for wideband signal transmission, even at severe aliasing conditions. Simulation results show that a generic memoryless nonlinear RF power amplifier with AMAM and AMPM distortion can be successfully identified at any sampling rates. Measurement results show the modeling error variation is less than 0.8dB over any sampling rates.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.286_287
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• 2009

In this paper, the protectability of distance relay is furtherly researched. Based on the probabilistic modeling of the measurement errors, the protectability of three zones is presented in detail by considering their different protection aims denoted by sensitivity and selectivity. The optimal setting for the each zone can be obtained to provide a reference for the practical application.

• Proceedings of the Korea Society for Simulation Conference
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• 2002.05a
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• pp.211-216
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• 2002

This paper focuses on the measurement of increased work efficiency expected from the information system through random interactions of the organizational behavioral factors whose attributes can be changed with the implementation of the information systems. Specifically the work reported here is concerned with modeling and analyzing the random interrelationships among the organizational behavioral factors which an information system will have impact on throughout the time horizon of its implementation in terms of office productivity. In addition, it is also concerned with developing a multi-factor analysis model based on random interactions to be used to assess the impact of information systems.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2528-2530
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• 2004

Neural network minimization problems are often conditioned and in this contribution way to handle this will be discussed. It is shown that a better conditioned minimization problem can be obtained if the problem is separated with respect to the linear parameters. This will increase the convergence speed of the minimization. One of the most powerful uses of neural networks is in function approximation(curve fitting)[1]. A main characteristic of this solution is that function (f) to be approximated is given not explicitly but implicitly through a set of input-output pairs, named as training set, that can be easily obtained from calibration data of the measurement system. In this context, the usage of Neural Network(NN) techniques for modeling the systems behavior can provide lower interpolation errors when compared with classical methods like polynomial interpolation. This paper solve of single-variable minimization using neural network.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.39-44
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• 2003

It was shown that the robustness of deterministic observers with respect to modeling errors, measurement bias and round-off errors can be represented by a single performance index the condition number of the observer eigenvector matrix. In this paper, a robust observer for multi-output systems is designed using the left eigenstructure assignment, where the observer gain can not be determined uniquely with respect to the desired observer poles. Utilizing the eigenstructuer assignment for the robustness of the observer, the desired eigenvector matrix is selected to achieve the observer eigenvector matrix with the small condition number. The performance of the designed robust observer is evaluated in a spindle-drive simulation example where the load speed to be estimated based on the measured signals.