• The Transactions of the Korean Institute of Electrical Engineers P
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• v.54 no.1
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• pp.34-40
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• 2005

This paper presents a frequency transfer function synthesis for simplifying a high-order model with time delay to a low-order model. A model reduction is based on minimizing the error function weighted by the numerator polynomial of reduced systems. The proposed method provides better low frequency fit and a computer aided algorithm. And in this paper, we present a design method of PID controller for achieving the desired specifications via the reduced model. The proposed method identifies the parameter vector of PID controller from a linear system that develops from rearranging the two dimensional input matrices and output vectors obtained from the frequency bounds.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.6
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• pp.439-444
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• 2002

In this paper, a new model reduction method is proposed to obtain a reduced order model in the frequency domain. The method is developed based on the second-order plus dead time modeling technique. The initial value of the reduced model parameters can be obtained using this method coinciding four point(0, -$\pi$/2, -$\pi$, -3$\pi$/2) on the Nyquist curve. The optimal parameters of the reduced model is obtained through calculation procedure with three steps. It is shown that Nyquist curves and unit step responses of the reduced models of numerical examples closely agree with those of original models.

• 제어로봇시스템학회:학술대회논문집
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• 1987.10b
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• pp.155-160
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• 1987

In this paper, the model reduction method of the linear time invariant continuous systems is proposed. The denominator of reduced order model is determined by the eigenvalue selected considering the error of the power series that exists between original system and reduced order system at each time moments. And the numerator of model is founded by the time moment matching method. The method suggested is compared with other various methods in examples.

• Journal of Satellite, Information and Communications
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• v.6 no.2
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• pp.46-50
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• 2011

In order to perform the satellite structural analysis, FE-Model(Finite Element Model) considering all mechanical properties is necessary. Generally, different companies develop several satellite components, and sometimes it is very difficult to obtain FE-Model. In this case, FE-Model reduction using superelement method can be good solution. For developing satellite, antenna manufacturer required satellite FE-Model to calculate microvibration induced by antenna operation, and condensed model using superelement method was provided. Superelement method is based on Craig-Bampton method, and it is applied to spacecraft FE-Model reduction in this paper. From modal analysis and the frequency response analysis results between full FE-Model and condensed model, the usefulness of reduced model is confirmed.

• International Journal of Highway Engineering
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• v.17 no.6
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• pp.11-18
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• 2015

PURPOSES : The purpose of this thesis is to evaluate the effectiveness of an active noise cancellation (ANC) system in reducing the traffic noise level against frequencies from the predictive model developed by previous research. The predictive model is based on ISO 9613-2 standards using the Noble close proximity (NCPX) method and the pass-by method. This means that the use of these standards is a powerful tool for analyzing the traffic noise level because of the strengths of these methods. Traffic noise analysis was performed based on digital signal processing (DSP) for detecting traffic noise with the pass-by method at the test site. METHODS : There are several analysis methods, which are generally divided into three different types, available to evaluate traffic noise predictive models. The first method uses the classification standard of 12 vehicle types. The second method is based on a standard of four vehicle types. The third method is founded on 5 types of vehicles, which are different from the types used by the second method. This means that the second method not only consolidates 12 vehicle types into only four types, but also that the results of the noise analysis of the total traffic volume are reflected in a comparison analysis of the three types of methods. The constant percent bandwidth (CPB) analysis was used to identify the properties of different frequencies in the frequency analysis. A-weighting was applied to the DSP and to the transformation process from analog to digital signal. The root mean squared error (RMSE) was applied to compare and evaluate the predictive model results of the three analysis methods. RESULTS : The result derived from the third method, based on the classification standard of 5 vehicle types, shows the smallest values of RMSE and max and min error. However, it does not have the reduction properties of a predictive model. To evaluate the predictive model of an ANC system, a reduction analysis of the total sound pressure level (TSPL), dB(A), was conducted. As a result, the analysis based on the third method has the smallest value of RMSE and max error. The effect of traffic noise reduction was the greatest value of the types of analysis in this research. CONCLUSIONS : From the results of the error analysis, the application method for categorizing vehicle types related to the 12-vehicle classification based on previous research is appropriate to the ANC system. However, the performance of a predictive model on an ANC system is up to a value of traffic noise reduction. By the same token, the most appropriate method that influences the maximum reduction effect is found in the third method of traffic analysis. This method has a value of traffic noise reduction of 31.28 dB(A). In conclusion, research for detecting the friction noise between a tire and the road surface for the 12 vehicle types needs to be conducted to authentically demonstrate an ANC system in the Republic of Korea.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.3
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• pp.420-424
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• 1987

The model reduction methods of the linear time invariant continuous systems are proposed. The energy dispersion method is used to obtain the model denominator. And the model numerator is found by the modified residue method or the time moment matching method. The methods suggested are compared with the method suggested by Lucas and give good results.

• Structural Engineering and Mechanics
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• v.61 no.6
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• pp.807-816
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• 2017

In this paper, we introduce an efficient new model reduction method, named the automated static condensation method, which is developed for the local analysis of large finite element models. The algebraic multilevel substructuring procedure is modified appropriately, and then applied to the original static condensation method. The retained substructure, which is the local finite element model to be analyzed, is defined, and then the remaining part of the global model is automatically partitioned into many omitted substructures in an algebraic perspective. For an efficient condensation procedure, a substructural tree diagram and substructural sets are established. Using these, the omitted substructures are sequentially condensed into the retained substructure to construct the reduced model. Using several large practical engineering problems, the performance of the proposed method is demonstrated in terms of its solution accuracy and computational efficiency, compared to the original static condensation method and the superelement technique.

• Journal of ILASS-Korea
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• v.20 no.1
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• pp.53-58
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• 2015

In this study, we prepare the Ag nanofluids synthesized by the chemical reduction method and measure the extinction coefficient of those nanofluids at a wavelength of 632.8 nm. The Ag nanofluids are synthesized by the chemical reduction method using silver nitrate ($AgNO_3$) and sodium borohydride ($NaBH_4$) in water and ethylene glycol (EG). For stable dispersion of Ag particles in the base liquids, polyvinyl pyrrolidone (PVP) is added as a surfactant. The extinction coefficient of manufactured Ag nanofluids is measured by an in-house developed measurement system at the wavelength of 632.8 nm. The results show that the extinction coefficient of water-based and EG-based Ag nanofluids is linearly increased with respect to the particle loadings. Moreover, it is shown that the extinction coefficient of EG-based Ag nanofludis is higher than that of water-based Ag nanofluids. Finally we compare the experimental results with both the Maxwell-Garnett model and Rayleigh scattering approximation model, and they demonstrate that the Rayleigh scattering approximation model is reasonably predict the extinction coefficient of Ag nanofluids using hydraulic diameter of silver nanoparticle.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1577-1582
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• 2011

Recently rapid construction of bridge is a main interest in construction. A research on rapid construction of pier coping is urgently needed because pier, which is a bridge understructure, directly affect lane reduction and increase of social cost. Precast assembly method and pre-assembly method are the main subjects of rapid construction. But these researches have focused not on reduction of reinforcement amount, but on modifying production method of coping. Reinforcement amount of design specification is as much as that of coping under constructing. So different approach is needed for reduction of reinforcement amount. In this paper, design of pier coping using strut-tie model was proposed for reduction of reinforcement amount and improvement of constructability. Railway bridge pier coping under constructing was analyzed using a finite element method and designed using strut-tie model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1370-1375
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• 2001

Substructure coupling or component mode synthesis may be employed in the solution of dynamic problems for structure. The model is partitioned into several subdomains. and a generalized Craig-Bampton representation is derived. In this paper the mode sets(normal modes. constraint modes) have been employed for model reduction. A generalized model reduction procedure has been described. Those reduction methods which adapt constraint modes have been described in detail. As examples. a flexible structure and a 10 DOF damped system are analyzed. Comparison with a conventional reduction method based on a complete model has been made via eigenpairs and dynamic responses.