• Journal of Korea Water Resources Association
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• v.46 no.1
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• pp.73-85
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• 2013

The researches on the parameter estimation for storage function method have been conducted for a long time using different methods. However, the determination of the optimal parameters takes a long time and there is a controversy that the proposed optimal parameters do not likely represent the physical characteristics of watershed. In this study, the characteristics of the continuity and storage function equation was analyzed and sensitivities were evaluated. As the result, the only optimal solution is suggested among several local optimums. It is also shown that the lag time is able to be determined using the direct runoff starting time of the watershed. From the sensitivity analysis, it is also proved that the determination of the lag time is very important and the only optimal solution could be found easily after selecting the lag time. Therefore, unlike the traditional optimization method, the proposed method does not take a long time to find the optimal solution which is depending on the characteristics of the rainfall events. The fixed coefficient method which is a method to estimate the optimal parameters of storage function method has been modified using the proposed method. Therefore, the practical efficiency to apply storage function method could be enhanced by applying the proposed method. While the traditional method takes care only the error of the runoff hydrograph, it is very important that the proposed method considers the characteristics of the watershed.

• Journal of the Korean Data and Information Science Society
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• v.17 no.4
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• pp.1091-1098
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• 2006

Park et al.(2005) and Choi et al.(2006) studied quick detection of variance change point for time series data in progress. For efficient detection they used moving variance ratio equipped with two tuning parameters; information tuning parameter p and lag tuning parameter q. In this paper, the moving variance ratio is studied under harsh conditions.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.11a
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• pp.135-142
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• 2000

The adjusting parameter set which enable control systems to locate on stability limit can be derived from theoretical or trial methods for an existing real system. The data from the results are much available to keep a system in the Proper stability condition even to site engineers who are inexperienced in the control system. In this paper, a general one loop control system was adopted for a model system the process of which was assumed to consist of a time-delay element and a first order-lag element in series. After obtaining the corresponding parameter set for the model system by mathematical procedures, their loci on the parameter space was taken according to frequency change. The parameter set loci of stability limit showed unique pattern, and particularity , the curves on the Kg-Ti parameter space were able to be generalized in the form of, an unique exponential formula. These properties were also compared with the results taken from experimental procedures by Nyquist response method and Ziegler & Nichols method on the time domain, and both results were confirmed to be nearly same.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.4
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• pp.34-42
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• 2004

In this paper, a double gimbal is used for roll/yaw attitude control of spacecraft and two feedback controllers are designed. One is a PD controller of no phase difference between roll and yaw control input. The other is a PD controller with a phase lag compensator about the yaw control input. The phase lag compensator is designed a first order system and a lag parameter is designed for the control of yaw angle. There are two case simulations for each of controllers; constant disturbance torques and initial errors of nutation. We obtain the results through simulations that a steady-state error and a rising time of yaw angle are developed by the compensator. In this paper, simulation parameters use the values of KOREASAT 1.

• Journal of Environmental Science International
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• v.15 no.4
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• pp.365-372
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• 2006

In this study investigated that topographical parametersestimate and calculated travel time, storage coefficient and lag time by watershed dividing 11, 8, 6 and 2. The results showed the more divide watershed, the more increase peak discharges. The results showed that Kraven-Clark-Kraven case is good simulated by compared observed data with calculated data. The sub-basin number are adequate $6{\sim}11$ for wichun and travel times compare observed data with calculated data at the younggok, to take about $18{\sim}20hr$ by simulated results but observed data shorter $8{\sim}10hr$. From this study results showed that it could be make narrow parameter estimate for observed hydrograph simulation, if more observed velocity and hydrograph. Also, as results of this study that is help to estimate parameters (arrival time, storage coefficient and lag time for Clark model.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.2
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• pp.351-356
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• 2001

In this paper, a general one-loop control system was assumed as a model system which has a time-delay element connected with a first order-lag element in series. After the corresponding parameter set causing stability limit condition for the model system was obtained by mathematical procedures, their loci on the parameter space was taken according of frequency change,. The parameter set loci of stability limit showed a specific pattern, and particularly the curves on the Kp-Ti parameter space were able to generalized in the form of an exponential formula. These properties were also compared with the results taken from experimental procedures by Nyquist response method and Ziegler & Nichols method on the time domain, and both results were confirmed to be nearly same.

• Proceedings of the Korean Society of Life Science Conference
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• 2008.10a
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• pp.64.1-64.1
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• 2008

• Water for future
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• v.28 no.4
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• pp.155-169
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• 1995

Three types of methods are used to determine the lag time which is an important parameter in estimating the geomorphological instantaneous unit hydrograph (GIUH) and their results are anlyzed hydrologically in this study. The first method uses only the average velocity and second one uses the combination of the stream length and the average velocity. The third method employs the relationship between watershed area and lag time obtained from the empirical coefficients of Boyd and Singh. To verify the applicabilities of such methods to the actual river basin, the obtained lag times were tested by using the observed data. The results showed that the first method was applicable to small watershed area but not to larger area. The several other hydrologic characteristics beside the watershed area should be considered for the third method because the accuracy of the lag time was not good. Finally, the second method gave the most similar simulation results and the best agreements to the observed runoff data than any other method.

• YAKHAK HOEJI
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• v.45 no.5
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• pp.506-512
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• 2001

Ketoprofen (KP) was formulated as a transdermal patch using the percutaneous penetration enhancers sorbitan monmmleate(SMO), polyvinylpyrrolidone(PVP). The control patch without penetration enhancers showed a KP flux of 8.9$\pm$0.75$\mu\textrm{g}$/$\textrm{cm}^2$/h The flux was increased in proportion to the concentration of SMO added. Furthermore, lag times were decreased upon addition of SMO. Conversely; the skin flux of KP was decreased in proportion to the concentration of PVP added. Pharmacokinetic parameters including $C_{max}$, $T_{max}$, and AUC were increased when SMO was added. However, $C_{mas}$ significantly decreased by the addition of PVP. $T_{max}$ was not significantly different in 2%, 4%, and 8% PVP patches. Patches containing 4% PVP showed the highest AUC value (19.158$\mu\textrm{g}$.h/ml). We found that the effectiveness of the two percutaneous penetration enhancers for topical KP patches was similar, with the addition of appropriate amounts of HPC modifying both skin flux and lag time of KP in the patches. In conclusion, it is possible to manufacture KP patches exhibiting high AUC, high skin flux, and short lag time using percutaneous penetration enhancers of SMO and PVP.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.7
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• pp.883-888
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• 2014

The paper describes the parameter tuning of power system stabilizer (PSS) for a power plant based on hybrid system modeling. The existing tuning method based on bode plot and root locus is well applied to keep power system stable. However, due to linearization of power system and an assumption that the parameter ratio of the lead-lag compensator in PSS is fixed, the results cannot guarantee the optimal performances to damp out low-frequency oscillation. Therefore, in this paper, hybrid system modeling, which has a DAIS (differential-algebraic-impusive-switched) structure, is applied to conduct nonlinear modeling for power system and find optimal parameter set of the PSS. The performances of the proposed method are carried out by time domain simulation with a single machine connected to infinite bus (SMIB) system.