• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.4
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• pp.633-642
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• 2021

Growing demand for electricity, when combined with the need to limit carbon emissions, drives a huge increase in renewable energy industry. In the electric power system, electricity supply always needs to be balanced with electricity demand and network losses to maintain safe, dependable, and stable system operation. There are three broad challenges when it comes to a power system with a high penetration of renewable energy: transient stability, small signal stability, and frequency stability. Transient stability analyze the system response to disturbances such as the loss of generation, line-switching operations, faults, and sudden load changes in the first several seconds following the disturbance. Small signal stability refers to the system's ability to maintain synchronization between generators and steady voltages when it is subjected to small perturbations such as incremental changes in system load. Frequency stability refers to the ability of a power system to maintain steady frequency following a severe system upset resulting in significant imbalance between generation and load. In this paper, we discusses these stability using system simulation by renewable energy deployment plan, and also analyses the influence of the renewable energy sources to the grid stability.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.109-117
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• 2008

In this study, a method predicting the displacement responseof structures from the measured dynamic strain signal is proposed by using a mode decomposition technique. Dynamic loadings including wind and seismic loadings could be exerted to the bridge. In order to examine the bridge stability against these dynamic loadings, the prediction of displacement response is very important to evaluate bridge stability. Because it may be not easy for the displacement response to be acquired directly on site, an indirect method to predict the displacement response is needed. Thus, as an alternative for predicting the displacement response indirectly, the conversion of the measured strain signal into the displacement response is suggested, while the measured strain signal can be obtained using fiber optic Bragg-grating (FBG) sensors. To overcome such a problem, a mode decomposition technique was used in this study. The measured strain signal is decomposed into each modal component by using the empirical mode decomposition(EMD) as one of mode decomposition techniques. Then, the decomposed strain signals on each modal component are transformed into the modal displacement components. And the corresponding mode shapes can be also estimated by using the proper orthogonal decomposition(POD) from the measured strain signal. Thus, total displacement response could be predicted from combining the modal displacement components.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.242-242
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• 2000

Comparing to the conventional adaptive filters using LMS algorithm, the proposed adaptive filters can reduce the amounts of computation and have robustness to variance of characteristics of input signals. LMS algorithm is performed in the domain of Hadamard transform after a reference signal and input signal are transformed by fast Hadamard transformation. As a transformation from time domain to Hadamard transformed domain, the proposed filter not only maintains the performance of estimating an input signal but also greatly reduces the number of multiplication. Moreover, the effect of characteristic changes of input signal is decreased. Computer simulation shows the stability and robustness of the proposed filter.

• Journal of Astronomy and Space Sciences
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• v.29 no.4
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• pp.389-395
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• 2012

The problem of spacecraft attitude control is solved using an adaptive neuro-fuzzy inference system (ANFIS). An ANFIS produces a control signal for one of the three axes of a spacecraft's body frame, so in total three ANFISs are constructed for 3-axis attitude control. The fuzzy inference system of the ANFIS is initialized using a subtractive clustering method. The ANFIS is trained by a hybrid learning algorithm using the data obtained from attitude control simulations using state-dependent Riccati equation controller. The training data set for each axis is composed of state errors for 3 axes (roll, pitch, and yaw) and a control signal for one of the 3 axes. The stability region of the ANFIS controller is estimated numerically based on Lyapunov stability theory using a numerical method to calculate Jacobian matrix. To measure the performance of the ANFIS controller, root mean square error and correlation factor are used as performance indicators. The performance is tested on two ANFIS controllers trained in different conditions. The test results show that the performance indicators are proper in the sense that the ANFIS controller with the larger stability region provides better performance according to the performance indicators.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7B
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• pp.652-659
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• 2006

The routing algorithm is one of the key research areas in ad hoc networks. The most of existing routing algorithms depends on current availability of wireless link when finding the feasible path. Dependence on current information may mislead to a fragile communication path. Some routing approaches that take statistical average on received signal power enhance the possibility to find the most stable path, but have limitation on considering only the average power level. In this paper, we propose routing algorithm based on link stability for ad hoc network. The proposed algorithm not only takes statistical average, but also traces the degree of variations in received signal power. The simulation result support that the proposed algorithm is more likely to find the most stable path under the severe communication environment.

• The Transactions of the Korea Information Processing Society
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• v.5 no.3
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• pp.715-719
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• 1998

In this paper, we propose a color enhancement system which is based on the improvement of transition time problem and specific color detection stability. The proposcd system apply the time difference correction step to corrects time difference which is taken place at the transimission process between color signal and color subcarrier signal and to reduce detection errors. And also, we proposed stability method to improve transition time problem and detection efficiency as the control of reference color. The proposed system controls specific color when the mean difference value of detected voltages greater than the value of minimum discriminate voltages of two adjacent color signals. Thus, the color enhancement system improves detection efficiency and controls specific color from the color signal without overlapping of correction range.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.9
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• pp.116-125
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• 2008

Inkjet printing technology with a drop-on-demand (DOD) inkget head technology has been recognized as one of versatile and low cost manufacturing tools in the electronics industry. Concerned with control of driving signal, however, general strategy to optimize jetting stability has not been understood well, because of the inherent complex multi-physics nature in inkjet phenomena. Motivated by this, present study investigates the effect of driving waveforms of piezoelectric head on jetting characteristics of DOD inkjet system focused on jetting stability with phase matching of pressure waves in the print head. The results show that velocities and volumes of the ink jetted droplets were linear relations with the driving signal's maximum voltage, while periodic behaviors are observed with the driving signal's pulse widths.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1444-1449
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• 2007

Inkjet printing technology with a drop-on-demand (DOD) inkjet head technology has been recognized as one of versatile and low cost manufacturing tools in the electronics industry. Concerned with control of driving signal, however, general strategy to optimize jetting stability has not been understood well, because of the inherent complex multi-physics nature in inkjet phenomena. Motivated by this, present study investigates the effect of driving waveforms of piezoelectric head on jetting characteristics of DOD inkjet system focused on jetting stability with phase matching of pressure waves in the print head. The results show that velocities and volumes of the ink jetted droplets were linear relations with the driving signal's maximum voltage, while periodic behaviors are observed with the driving signal's pulse widths.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.10
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• pp.1413-1421
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• 1993

It is possible to weaken the undesirable effect of a bounded control input signal to the plant and done by setting up an additional correction loop which compensates for the suppresed portion of the control input signal. The design and analysys of stability of state controller is used by the Kalman-Szego-Lemma and as the result of this method is made possible to take advantage of the control input to the plant even for small error signals.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.139-141
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• 2002

This paper describes a new contingency analysis methods for small signal security assessment based on the eigenvalue perturbation. The eigenvalue perturbation with respect to MW changes can be used to find possible sources of the low frequency oscillation, and to select contingency for small signal stability. The proposed algorithm has been successfully tested on the KEPCO systems.