• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.750-753
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• 2005

An equivalent linearization technique based on Rayleigh peak distribution for friction damper and brace system (FDBS) under stochastic excitation is proposed. For verification, shaking table test of a small scale 3-story building model with the FDBS is conducted for various slip moment levels. Using experimental result, equivalent linearization of the FDBS is conducted based on Rayleigh peak distribution, which is compared with measured peak distribution. For comparative study, model updating technique is applied based on identified modal properties. Finally, complex modal analysis and time history analysis for the obtained equivalent linear systems are conducted and compared with experimental result

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.890-895
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• 2002

The equivalent electroacoustic circuit approach has been conventionally used for estimating the absorption coefficient of a single layer perforated plate system. When the single layer system is extended to the multiple layer ones, however, it is found that an analogy error has been involved in the equivalent electroacoustic parallel circuit approach proposed by previous investigators. The analogy error is demonstrated by the corrected equivalent electroacoustic circuit approach in this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.387.2-387
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• 2002

The equivalent electroacoustic circuit approach has been conventionally used for estimating the absorption coefficient of a single layer perforated plate system. When the single layer system is extended to the multiple layer ones, however, it is found that an analogy error has been involved in the equivalent electroacoustic parallel circuit approach proposed by previous researchers. The analogy error is demonstrated by the corrected equivalent electroacoustir circuit approach proposed en this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.304-308
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• 2006

The focus of this study is modeling technique for a bellows in vehicle exhaust system. Bellows was developed using tile finite element model by replacing with the equivalent beam. The equivalent beam model were studied in detail. Non-structural node in the cross section of original model is given to expressing their motion. Equivalent mass matrix and stiffness matrix calculated using Guyan reduction method. Material Properties of beam was obtained from the direct comparison between equivalent model and that of Timoshenko beam model. The calculated natural frequencies and mode shape are compared with the reference results and coincided well. The results were compared with the confirmed results, which were in good agreement.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.11
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• pp.1170-1176
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• 2008

In this study, we propose a new method to control both the beat clarity and beat period in a ring structure. An equivalent ring which satisfies the measured mode condition is determined by using the equivalent ring theory. Theoretical analysis and finite element analysis on the equivalent ring are performed to investigate the effect of the local structural modification on the beat clarity and beat period. Beat clarity and period are improved by attaching asymmetric mass or decreasing local thickness. Through the analysis on the equivalent ring, the proper position and the amount of the local variation are determined to satisfy the required clarity and period condition. All the analysis results are compared and verified by the experiment.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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• pp.394-403
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• 2006

A new equivalent linearization technique is proposed for a friction damper-brace system (FDBS) idealized as a elastoplastic system. The equivalent linearization technique utilizes secant stiffness and dissipated energy defined by the probability distribution of the extremal displacement of the FDBS. In addition, a conversion scheme is proposed so that an equivalent linear system is designed first and converted to the FDBS. For comparative study, an existing model update technique based on system identification is modified in a form appropriate to update single element. For the purpose of verification, shaking table tests of a small scale three-story shear building model, in which a rotational FDBS is installed, are conducted and equivalent linear systems are obtained using the proposed technique and the model update technique. Complex eigenvalue analysis is conducted for those equivalent linear systems, and the natural frequencies and modal damping ratios are compared with those obtained from system identification. Additionally, RMS and peak responses obtained from time history analysis of the equivalent linear systems are compared with measured ones.

• Journal of the Korean Home Economics Association
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• v.43 no.4 s.206
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• pp.31-47
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• 2005

This study is a preliminary investigation into improving the environmental quality of schools. The purpose was to clarify the present conditions and reasons of noise in elementary schools located near airports and roads by noise level measurements and questionnaire surveys of subjective responses. fold measurements on equivalent and instantaneous noise levels, indoor and outdoor, were carried out in 3 schools during the periods 11th~ 13th of February and 2nd~ 7th of July,2003. The respondents were 94 teachers working in the 3 schools. The results were as follows. 1) Indoor noise levels of the 3 schools were 36.g~73 dB(A) in winter, and 46.9~ 91 dB(A) in summer. These values were higher than the indoor noise standard of 50 dB(A), except for the average of equivalent noise levels in winter.2) Outdoor noise levels of the schools were 41.1 ~ 101 dB(A) in winter, and 52.4~ 102 dB(A) in summer. These values were generally inappropriate relative to the standard for environmental noise of 65 dB(A). 3) The respondents showed relatively non- positive responses during school hours for interruptions by environmental noise.4) The frequently checked types of environmental noise of the schools were 'airplane noise','surrounding facilities', and 'traffic noise'. The frequently checked types of damage by environmental noise were 'Interrupting school hours' and 'Interrupting business'.

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.2
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• pp.1-13
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• 1981

Simple models for analyzing noise factors have been derived for four fundamental types of feedback amplifiers. These models have been obtained by changing equivalent noise sources of feedback networks into equivalent input noise sources of basic amplifiers. They are used to analyse noise factors for these amplifiers. Noise tractors measured for the four types of feedback amplifiers agree with theoretical results.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.4
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• pp.342-348
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• 2013

In this paper, the evaluation method for the responsivity and noise characteristics of an infrared thermal imaging camera was presented. Signal transfer function and noise equivalent temperature difference of the infrared thermal imaging camera were obtained by using a differential mode blackbody that is able to control the temperature difference ${\Delta}$T between an infrared target and its background. And we verified the suitability of our evaluation method through comparison between the found noise equivalent temperature difference and the specification of the camera. In addition, the difference of 0.01 K of the two noise equivalent temperature differences calculated from with and without nonuniformity correction suggests that the nonuniformity correction is essential process for the evaluation of the infrared thermal imaging camera.

• ETRI Journal
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• v.27 no.5
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• pp.628-634
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• 2005

From AC analysis results utilizing a 2-dimensional device simulator, we extracted an AC-equivalent circuit of a grounded-gate NMOS (ggNMOS) electrostatic discharge (ESD) protection device. The extracted equivalent circuit is utilized to analyze the effects of the parasitics in a ggNMOS protection device on the characteristics of a low noise amplifier (LNA). We have shown that the effects of the parasitics can appear exaggerated for an impedance matching aspect and that the noise contribution of the parasitic resistances cannot be counted if the ggNMOS protection device is modeled by a single capacitor, as in prior publications. We have confirmed that the major changes in the characteristics of an LNA when connecting an NMOS protection device at the input are reduction of the power gain and degradation of the noise performance. We have also shown that the performance degradation worsens as the substrate resistance is reduced, which could not be detected if a single capacitor model is used.