• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.9
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• pp.1827-1833
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• 2009

This paper deals with the trajectory tracking control of wheeled mobile robots with input constraint. The proposed method converts the trajectory tracking problem to the system stability problem using the control inputs composed of feedforward and feedback terms, and then, by using Taylor series, nonlinear terms in origin system are transformed into polynomial equations. The composed system model can make it possible to obtain the control inputs using numerical tool named as SOSTOOL. From the simulation results, the mobile robot can track the reference trajectory well and can have faster convergence rate of the trajectory errors than the existing nonlinear control method. By using the proposed method, we can easily obtain the control input for nonlinear systems with input constraint.

• Journal of Power Electronics
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• v.15 no.1
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• pp.96-105
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• 2015

In recent years, the multilevel converters have been given more attention due to their modularity, reliability, failure management and multi stepped output waveform with less total harmonic distortion. This paper presents a novel symmetric multilevel inverter topology with reduced switching components to generate a high quality stepped sinusoidal voltage waveform. The series and parallel combinations of switches in the proposed topology reduce the total number of conducting switches in each level of output voltages. In addition, a comparison between the proposed topology with another topology from the literature is presented. To verify the proposed topology, the computer based simulation model is developed using MATLAB/Simulink and experimentally with a prototype model results are then compared.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.2911-2913
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• 1999

This paper suggest an optimal identification method to complex and nonlinear system modeling that is based on Fuzzy-Neural Network(FNN). The FNN modeling implements parameter identification using HCM algorithm and optimal identification algorithm structure combined with two types of optimization theories for nonlinear systems, we use a HCM Clustering Algorithm to find initial parameters of membership function. The parameters such as parameters of membership functions, learning rates and momentum coefficients are adjusted using optimal identification algorithm. The proposed optimal identification algorithm is carried out using both a genetic algorithm and the improved complex method. Also, an aggregate objective function(performance index) with weighted value is proposed to achieve a sound balance between approximation and generalization abilities of the model. To evaluate the performance of the proposed model, we use the time series data for gas furnace, the data of sewage treatment process and traffic route choice process.

• Journal of Korean Society for Quality Management
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• v.21 no.1
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• pp.181-189
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• 1993

Over the past two decades, forecasting has gained widespread acceptance as an integral part of business planning and decision making. Accurate forecasting is a prerequisite to successful planning. Accordingly, recent advances in forecasting techniques are of exceptional value to corporate planners. But most of forecasting mothods are reveal its limit and problem for precision and reliability duing to each relationship for raw data and possibility of explanation for each variable. Therefore, to construct the Integrated Forecasting Model(IFM) for Information Factor Analysis, it shoud be considered that whether law data has time lag and variables are explained. For this. following several method can be used : Least Square Method, Markov Process, Fibonacci series, Auto-Correlation, Cross-Correlation, Serial Correlation and Random Walk Theory. Thus, the unified property of these several functions scales the safety and growth of the system which may be varied time-to-time.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.2
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• pp.241-249
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• 2009

It is well known that the trend of water demand in large-size water supply systems has been suddenly changed, and many expansions of water supply facilities become unnecessary. To be cost-effective, thus, politicians as well as many professionals lay stress on the adaptive management of water supply facilities. Failure in adapting to the new trend of demand is sure to be the most critical reason of unnecessary expansions. Hence, we try to develop the model and modeling procedure that do not depend on the old data of demand, and provide engineers with the fast learning process. To forecast water demand of Seoul, the Bayesian parameter estimation was applied, which is a representative method for statistical pattern recognition. It results that we can get a useful time-series model after observing water demand during 6 years, although trend of water demand were suddenly changed.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.39 no.1 s.119
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• pp.8-15
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• 2007

In an effort to develop control strategies for the wet-end of paper machines, dynamic models for retention and formation processes have been developed. The retention process, including headbox total and filler consistencies, white water total and filler consistencies, the basis weight and the ash content of paper, can be modeled from first-principles (mass balances). To include the effect of wet-end chemistry variables, first-pass retention was included as a parameter dependent on operating conditions. In addition, dynamics of formation was simulated by developing an empirical model of formation and coupling with the dynamic models for the retention process. A series of experiments were performed using a pilot paper machine. The experimental results and the model predictions showed relatively good agreement.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.2
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• pp.85-94
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• 1994

The cutting mechanism of ultrasonic vibration machining is characterized as two phases, that is, an impact at the cutting edge and a reduction of cutting force due to non-contact interval between tool and workpiece. In this paper, in order to identify cutting dynamics of a system with ultrasonically vibrated cutting tool, an ARMA modeling is performed on experimental cutting force signals which have a dominant effect on cutting dynamics. The aim of this study is, through Dynamic Date System methodology, to find the inherent characteristics of an ultrasonic vibration cutting process by considering natural frequency and damping coefficient. Surface roughness and stability of cutting process under ultrasonic vibration are also considered

• The Mathematical Education
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• v.51 no.4
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• pp.429-453
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• 2012

The purpose of the study were to analyze teaching models of arithmetic operations of integers in Korean middle school mathematics textbooks of the first grade and Americans', from which we compare and analyze standards for choice of models of middle school teachers and preservice mathematics teachers. We also analyze the effect of the choice of teaching models for students to understand and appreciate number systems as a coherent body of knowledge. On the basis of that, we would like to find the best model to help students understand and reason the process of formulate the arithmetic operations of natural numbers and integers into the operation of the real number system. Furthermore, we help these series of the study to be applied effectively in the middle school mathematics class in Korea.

• Korean Journal of Geomatics
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• v.4 no.1
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• pp.9-16
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• 2004

An object-oriented design was carried out for the digital photogrammetric processes. Classes were identified and implemented to develop an integrated digital photogrammetry system using a 3 dimensional self-calibration model for CCD cameras. This integrated system is deemed to be a significant progress from the conventional photogrammetric system which is a series of discrete processes. Object oriented methodology was selected for the implementation of the integrated photogrammetric system because it would be a very complex task to get the same result using a procedural programming language. Besides the simplification of development effort, object oriented methodology has further benefits of better management of program in case when updates to parts of the program are necessary. Using the classes designed in this study, a 3 dimensional self-calibration model was developed for a CCD camera. Classes for data input and image handling as well as classes for bundle adjustment were implemented. The bundle adjustment system was further enhanced with member functions to handle additional parameters for principal point coordinates and focal length, thereby, enabling the application to non-metric CCD cameras.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.3
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• pp.187-194
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• 1999

In this study, a series of items on the safety and stability of cracked main structure in subway are investigated and analyzed. Cracks due to dry contraction under the construction can be found when a tensile stress of cross section is higher than tensile strength at a value of coefficient of dry contraction $200{\times}10^{-6}$. It is concluded that there is no problems when load carrying capacity, that is, an ability of resisting loads of structure is enough in this analytical model. Also, it is concluded that this model has a desirable serviceability because a width of bending crack is lower than allowable one.