• Journal of IKEEE
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• v.24 no.1
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• pp.106-119
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• 2020

In this paper, we propose a control scheme for quadrotor system using a pole placement method. When using a state feedback controller, a lot of trial and error in selection of control gains are often required to improve system performance. In order to relax this complicated process, we analyze the closed-loop system associated with control gains. Then, we present a control gain selection algorithm for control gains using a pole placement method to improve the system performance. The proposed control method is applied to the actual quadrotor system to illustrate the validity of the proposed method.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.7
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• pp.142-149
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• 2009

The aim of this study was to identify both the mechanical and reflex properties associated with spasticity in hemiplegic patients. Ten hemiplegic patients were included in this study. Multiple pendulum tests were executed for each subject, and knee joint angle and EMG of Rectus Femoris muscle were measured. The neuromusculoskeletal system model was developed from generally accepted mechanism and identified through minimization of the error in the model-predicted pendulum trajectories. The identification was successful in terms of small error in simulated kinematics and high sensitivity and precision of simulated torque against EMG activity. The reflex threshold showed significant difference between different clinical scores (p<0.01) and significant negative correlation (r=-0.93) with the EMG duration. It is expected that the suggested method may help in understanding mechanisms underlying spasticity.

• Journal of the Korean Institute of Intelligent Systems
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• v.9 no.6
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• pp.591-597
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• 1999

When fuzzy logic controllers which are designed based on plant models and intuitive base are applied to real plants, the control systems may not give satisfactory control results due to the modeling error and the lack of knowledge on the plants. In that case. the controller must be retuned by adjusting the control parameters; this retuning process may require a large number of trial-and-error evaluations and thus much time and cost. In order to resolve these problems, we propose a systematic and efficient procedure for designing a fuzzy logic controller using response surface methodology. First wc select the initial optimal conditions of control parameters using a genetic algorithm, in which a nominal plant model with intrinsic modeling errors is used. And then we determine the tinal optimal conditions of the control parameters using response surface methodology. Computer simulations are performed to verify the capability of the proposed method.

• Journal of the Korean Society of Visualization
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• v.21 no.2
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• pp.63-71
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• 2023

Energy storage and distribution technologies are emerging as important factors as research on renewable energy continues. Analyzing the thermal flow of phase change material inside a latent heat storage device and to predict the phase change time is an important part for improvement of thermal performance. However, most of the current research is based on the trial-and-error experimental investigation to measure the phase change time. Therefore, in this study, a can-type phase change material container was designed, and the numerical method for analyzing the thermal flow of phase change material was established and validated. The error rate of the phase change time between the numerical and experimental results was within 5%, which proves its reliability. As a result, the phase change finishing times were found to be 78 minutes with inlet fluid temperature of 80℃ during charging process, and 126 minutes with inlet fluid temperature of 9℃ during discharging process.

• Journal of Navigation and Port Research
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• v.36 no.8
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• pp.637-641
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• 2012

In this paper, the method that reduce a computation time by optimizing computation process is proposed to realize low-power underwater acoustic communication system. At first, dependency of decision delay on tap length of linear equalizer was investigated. Variance is calculated based on this result, and the optimal decision delay bound is estimated. In addition to decide optimal tap length with decision delay, we extracted the MSE(Mean Square Error) graph. From the graph, we obtained variance value of the MSE-decision delay, and estimated the optimum decision delay range from the variance value. Also, using the extracted optimal parameters, we performed a simulation. According to the result, the simulation employing optimal tap length, which is only 40% of maximum tap length, showed a satisfactory performance comparable to simulation employing maximum tap length. We verified that the proposed method has 33% lower tap length than maximal tap length via sea trial.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.627-632
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• 2008

The cross sectional shape of intermediate die is one of important parameters to improve dimensional accuracy of final product in shaped drawing process. Until now, it has been designed by the experience or trial and error of the expert. In this study, the cross sectional shape of intermediate die for spline shape is determined by the electric fields analysis and scale factor method. The result of the electric fields analysis and scale factor method have been compared with that of the expert method. The effects of cross sectional shape on the dimensional accuracy were investigated by using FE-simulation. And then the multi-stage shaped drawing experiments were performed to verify the results of FE-simulation. As a result, the cross sectional shape from the electric fields analysis and scale factor method had the good dimensional accuracy. These two methods can be used for the method to obtain the cross sectional shape of intermediate die in shaped drawing process.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.4
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• pp.9-19
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• 2016

The objective of this study was to evaluate the applicability of SWAT (Soil and Water Assessment Tool) model for runoff estimation in the Nam river dam watershed. Input data for the SWAT model were established using spatial data (land use, soil, digital elevation map) and weather data. The SWAT model was calibrated and validated using observed runoff data from 2003 to 2014 for three stations (Sancheong, Shinan, Changchon) within the study watershed. The $R^2$ (Determination Coefficient), RMSE (Root Mean Square Error), NSE (Nash-Sutcliffe efficiency coefficient), and RMAE (Relative Mean Absolute Error) were used to evaluate the model performance. Parameters for runoff calibration were selected based on user's manual and references and trial and error method was applied for parameter calibration. Calibration results showed that annual mean runoff were within ${\pm}5%$ error compared to observed. $R^2$ were ranged 0.64 ~ 0.75, RMSE were 2.51 ~ 4.97 mm/day, NSE were 0.48 ~ 0.65, and RMAE were 0.34 ~ 0.63 mm/day for daily runoff, respectively. The runoff comparison for three stations showed that annual runoff was higher in Changchon especially summer and winter seasons. The flow exceedance graph showed that Sancheong and Shinan stations were similar while Changchon was higher in entire fraction.

• Journal of Environmental Science International
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• v.29 no.8
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• pp.793-800
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• 2020

The conventional development of multi-component electrodes is based on the researcher's experience and is based on trial and error. Therefore, there is a need for a scientific method to reduce the time and economic losses thereof and systematize the mixing of electrode components. In this study, we use design of mixture experiments (DOME)- in particular a simplex lattice design with Design Expert^Ⓡ program- to attempt to find an optimum mixing ratio for a three-component electrode for the high RNO degradation; RNO is an indictor of OH radical formation. The experiment included 12 experimental points with 2 center replicates for 3 different independent variables (with the molar ratio of Ru, Ti, Ir). As the Prob > F value of the 'Quadratic' model is 0.0026, the secondary model was found to be suitable. Applying the molar ratio of the electrode components to the corrected response model results is an RNO removal efficiency (%) = 59.89 × [Ru] + 9.78 × [Ti] + 67.03 × [Ir] + 66.38 × [Ru] × [Ir] + 132.86 × [Ti] × [Ir]. The R² value of the equation is 0.9374 after the error term is excluded. The optimized formulation of the ternary electrode for an high RNO degradation was acquired when the molar ratio of Ru 0.100, Ti 0.200, Ir 0.700 (desirability d value, 1).

• Water for future
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• v.27 no.4
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• pp.59-67
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• 1994

The objective of this study is to develop a method which can design an optimal pipe network system using nonlinear programming(NLP) technique. The method finds the minimum-cost pipe network while satisfying all the design constraints including hydraulic constraints. The method developed in this study was applied to the Goyang distribution area in Goyang, Kyoungi-do. It has been found in the application and the comparison between the original design and the optimal design of this study that the optimal design method developed in this study does not require the trial-and-error procedure while satisfying the discharge and pressure requirements at the demanding nodes. Therefore, the optimal design method using NLP could be effectively utilized in the practical design considering economic aspect of the pipe network system at the same time.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.428-432
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• 2003

Quantitative Feedback Theory (QFT) is one of most effective methods of robust controller design and can be considered as a suitable method for systems with parametric uncertainties. Particularly it allows us to obtain controllers less conservative than other methods like $H_{\infty}$ and ${\mu}$-synthesis. In QFT method, we transform all the uncertainties and desired specifications to some boundaries in Nichols chart and then we have to find the nominal loop transfer function such that satisfies the boundaries and has the minimum high frequency gain. The major drawback of the QFT method is that there is no effective and useful method for finding this nominal loop transfer function. The usual approach to this problem involves loop-shaping in the Nichols chart by manipulating the poles and zeros of the nominal loop transfer function. This process now aided by recently developed computer aided design tools proceeds by trial and error and its success often depends heavily on the experience of the loop-shaper. Thus for the novice and First time QFT user, there is a genuine need for an automatic loop-shaping tool to generate a first-cut solution. In this paper, we approach the automatic QFT loop-shaping problem by using an algorithm involving Linear Programming (LP) techniques and Genetic Algorithm (GA).