• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.90-92
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• 1993

Stability analysis is an essential work in the operation and planning of power system. There are two categories, direct method and indirect method, and indirect method calculates the trajectories of states by numerical methods. Popular method using explicit integration has relatively low accuracy, so a more accurate method is requested. By the consideration of bus voltage variation, Runge-Kutta 4th order method can be made more accurate, but this scheme need much computation time. Through three recipes, computational cost of proposed method can be reduced. So the proposed method has improved accuracy and slight rise in cost. the method was tested on the IEEE 14 bus system.

• Journal of the Korean Mathematical Society
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• v.33 no.2
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• pp.235-247
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• 1996

Many numerical computations in science and engineering can only be solved approximately since the available infomation is partial. For instance, for problems defined ona space of functions, information about f is typically provided by few function values, $N(f) = [f(x_1), f(x_2), \ldots, f(x_n)]$. Knwing N(f), the solution is approximated by a numerical method. The error between the true and the approximate solutions can be reduced by acquiring more information. However, this increases the cost. Hence there is a trade-off between the error and the cost.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.36-47
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• 1999

Three-way catalyst converter, cleaning up the exhaust gas contamination of SI engine, has the best efficiency when A/F ratio is near the stoichiometry . The feedback control using oxygen sensors in the exhaust manifold has limits caused by the system delays. So the accurate measurement of air flow rate to an engine is essential to control the fuel injection rate especially on transient condition like the rapid throttle opening and closing. To measure the rapid change of flow rates. the air flow meter for the engine requires quick response, flow reversal detection, and linearity . Tjhe proposed integration type air flow meter (IFM), composed of an ultrasonic flow meter with an integration circuit, has significantly improved the measurement accuracy of air mass inducted through the throttle body. The proposed control method estimated the air mass at the cylinder port using the measured air mass at the throttle . For the fuel dynamic model, the two constant fuel model is introduced . The control parameters from air and fuel dynamics are tuned to minimize the excursion of the air fuel ratio. As a result A/F ratio excursion can be reduced within 5% when throttle rapidly opens and closes at the various engine conditions.

• Journal of Forest and Environmental Science
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• v.29 no.4
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• pp.307-313
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• 2013

Forest Survey consists of road survey, topographic survey, tree mapping survey, stream survey and also ridge survey. Information from forest survey is important and become essential in preparing base map to be used for forest harvesting planning and control. With the current technologies technique of data processing and mapping from traditionally hand drawn method had shifted to a computer system particularly the use of Computer Aided Design (CAD). This gives great advantages to the forest managers and logging operators. However data processing and mapping duration could be further reduced by integrating CAD with other established software such as Microsoft Excel. This time study to show that there is significance difference in term of duration for data processing and efficiency using AutoCAD in combination with Microsoft Excel program as compare to the use of AutoCAD program alone. From the study, it shows that the integration of AutoCAD and Microsoft Excel is able to reduce 70% of duration for data processing and mapping as compared to the use of AutoCAD program alone.

• Plant Journal
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• v.8 no.3
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• pp.55-63
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• 2012

This study aims to suggest the improved business process by analyzing the current design process on work flow of the 3D design of power plant, drawing a problems and setting the improving direction through the integration method of the business process reengineering(BPR). In order to realize the improved business process, the integrated design performance system focused on the 3D design was established and accordingly the study analyzed cases of project performances through the integration system and drew the improved effects quantitatively. In the result of the project performance applied with the 3D design integration system, it showed 20.4% design cost saving effect for appropriate rated cost and the integration of design information from each design parts, sub contracters and vendors reduced overlapped works and improved the consistency of repeated design alteration.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.20 no.43
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• pp.211-218
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• 1997

Since Industrial Revolution, the sudden industrialization and population explosion have brought about a serious environmental pollution on the air of the earth, the quality of water and the soil, and the greenhouse effect by the destruction of the ozone layer and the greenhouse gas, the organism diversity decline, the desertification by the ruining of woods and the overall global environmental pollution such as the contamination of the ocean and rivers have been come to the front. So the new recognition on the environment is being spreaded in construction business and the efforts for certification acquisition of ISO 14000 being followed by ISO 9000 are progressing, Accordingly, with an example of H Company where integration system is built so that it can minimize the efforts and cost at the construction of the management system, operation and management after the fact, this paper shall suggest the practical scheme of 3 steps through a study to integrate both existing quality management system and new environmental management system. As the integration system of the quality and environment which is constructed by this method is executed, the number of the established and managed document is cut by about a third and so the disorder to encounter between these documents is prevented and unnecessary efforts is reduced in constructing a system, consequently the efficiency of the system is accomplished. Also as the dualization of quality management system and environmental management system additionally needs more men and money after certification acquisition, the non-construction of the integration system may give rise to a cause to aggravate the burden of the company and hereafter when a new system is imported, it may be very difficult to integrate the system. This system integration enables a efficient and effective system to be constructed , operated , and managed after the fact.

• Honam Mathematical Journal
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• v.43 no.3
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• pp.373-383
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• 2021

In this study, a numerical method deals with the Chebyshev wavelet collocation and Adomian decomposition methods are proposed for solving Korteweg-de Vries equation. Integration of the Chebyshev wavelets operational matrices is derived. This problem is reduced to a system of non-linear algebraic equations by using their operational matrix. Thus, it becomes easier to solve KdV problem. The error estimation for the Chebyshev wavelet collocation method and ADM is investigated. The proposed method's validity and accuracy are demonstrated by numerical results. When the exact and approximate solutions are compared, for non-linear or linear partial differential equations, the Chebyshev wavelet collocation method is shown to be acceptable, efficient and accurate.

• Structural Engineering and Mechanics
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• v.38 no.4
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• pp.429-441
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• 2011

In large-scale problem, a huge size of computational resources is needed for a reliable solution which represents the detailed description of dynamic behavior. Recently, eigenvalue reduction schemes have been considered as important technique to resolve computational resource problems. In addition, the efforts to advance an efficiency of reduction scheme leads to the development of the multi-level system condensation (MLSC) which is initially based on the two-level condensation scheme (TLCS). This scheme was proposed for approximating the lower eigenmodes which represent the global behavior of the structures through the element-level energy estimation. The MLSC combines the multi-level sub-structuring scheme with the previous TLCS for enhancement of efficiency which is related to computer memory and computing time. The present study focuses on the implementation of the MLSC on the direct time response analysis and the frequency response analysis of structural dynamic problems. For the transient time response analysis, the MLSC is combined with the Newmark's time integration scheme. Numerical examples demonstrate the efficiency of the proposed method.

• Advances in Computational Design
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• v.8 no.3
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• pp.237-253
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• 2023

Torque ripple content and variable switching frequency operation of conventional direct torque control (DTC) are reduced by the integration of space vector modulation (SVM) into DTC. Integration of space vector modulation to conventional direct torque control known as SVM-DTC. It had been more frequently used method in renewable energy and machine drive systems. In this paper, SVM-DTC is used to control the rotor side converter (RSC) of a wind driven doubly-fed induction generator (DFIG) because of its advantages such as reduction of torque ripples and constant switching frequency operation. However, flux and torque ripples are still dominant due to distorted current waveforms at different operations of the wind turbine. Therefore, to smoothen the torque profile a Neural Network Controller (NNC) based SVM-DTC has been proposed by replacing the PI controller in the speed control loop of the wind turbine controller. Also, stability analysis and simulation study of DFIG using process reaction curve method (RRCM) are presented. Validation of simulation study in MATLAB/SIMULINK environment of proposed wind driven DFIG system has been performed by laboratory developed prototype model. The proposed NNC based SVM-DTC yields superior torque response and ripple reduction compared to other methods.

• International Journal of Aeronautical and Space Sciences
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• v.9 no.1
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• pp.85-99
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• 2008

The dynamic response analysis for large structures using finite element method requires a large amount of computational resources. This paper presents an efficient vibration analysis procedure by combining node-based substructuring reduction method with a response analysis scheme for structures with undamped, proportional or nonproportional damping. The iterative form of substructuring reduction scheme is derived to reduce the full eigenproblem and to calculate the dynamic responses. In calculating the time response, direct integration scheme is used because it can be applied directly to the reduced model. Especially for the non proportional damping matrix, the transformation matrices defined in the displacement space are used to reduce the system. The efficiency and the effectiveness of the present method are demonstrated through the numerical examples.