• Proceedings of the KSR Conference
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• 2002.10a
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• pp.182-187
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• 2002

Since most of main noise sources of the railroad vehicle are transmitted to the passenger's ear through the vibration of the panel, the insulation performance of the panels should be high enough to protect the passengers from the noisy environment. Specifically, the composite materials which are generally used for reducing the weight of the vehicle compartment have the low insulation performance, noise control actions should be taken appropriately by considering the insulation performance of the panels. In this study, the insulation performances of the inner/outer panels were evaluated and the contribution of the aluminum door was estimated compared to the composite panels. The results can furnish an indepth understanding of the insulation characteristics of the panel of railroad vehicle.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.11
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• pp.996-1002
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• 2013

Conditions of stiffness for a steel spring torsional vibration damper are difficult and ambiguous. Nevertheless correct estimation of stiffness is essential and important in the damper design for the damper to activate properly in the field. In this paper, to build up the estimation method of steel spring torsional vibration damper a miniaturized model was developed for modelling between a spring and inner star of the damper. The method obtained from the results through the experiment and analysis of it was applied to the prototype torsional damper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1099-1103
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• 2001

In room acoustics, reverberation time (RT) is the most important and general factor that represents character of room or inner space. However, RT, especially in low frequency range, can have the different value according to the measuring points and methods. This study comprehends the cause of error occurring dominantly in low frequency range when RT is measured and examines that the each error of RT measured in the cabin and reverberation chamber having different properties, influences what extent on sound transmission loss (STL)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.414-421
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• 1996

The study of the vibration characteristics of annular sector plates which are clamped along their inner circumferential edge is important for structural engineers. The present analysis consists of experimental method and numerical method. The experimental method using time-average holographic interferometry is obtained vibration modes and frequencies. The experimental results are verified by a numerical method using F.E.M. The important aspects of the present paper is the dependence of the natural frequencies and the mode shape on the annular area changing sector angle. The radial nodal lines converge to the center of the plate. As increasing sector angle, the radial modes are predominant.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.6
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• pp.484-489
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• 2003

The paper represents stability of a rotor system with the squeeze film damper (SFD) using an electromagnet. The electromagnet is installed in the inner damper of the SFD. The proposed SFD has basically the property of a conventional SFD and variable damping property according to variation of the applied electric current. Therefore, when the applied current Is controlled, the whirling vibration of the rotor system can be effectively reduced in a wide operational speed range. In the present work, the performance of the SFD was experimentally investigated according to changing the magnetic field strength. As the applied current increased, damping ratios increased, while whirling amplitudes greatly reduced.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.333-336
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• 2004

This paper presents performance of the impact hammer drill with coefficient of restitution, lubrication and friction, pressure leakage, damper efficiency and the general quality test. The novel measurement systems are introduced in order to get the reasonable data. The mechanism of strikers with inner pressure is revealed in the general quality test. Due to these factors we are able to make the computational analysis correctly.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.543-543
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• 2010

The objective of this research is estimating the location of interested sound source by using the similarity between a beamformer output in time domain and the candidate signal. The waveform of beamformer output at the location of sound source is similar with the waveform emitted by that source. To estimate the location of sound source by using this feature, we define quantified similarity between candidate signal and beamformer output. The candidate signal describes the signal which is generated by interested source. In this paper, similarity is defined by four methods. The two methods use time vector comparison, and the other two methods use time-frequency map or linear prediction coefficients. To figure out the results and performance of localization by using similarities, we demonstrate two conditions. The one is when two pure tone sources exist and the other condition is when several bird sounds exist. As a consequence, inner product with two time-vectors and structural similarity with spectrograms can estimate the locations of interest sound source.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.404-409
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• 2004

A compressor loop pipe is the most important part in a refrigerator from the view of structural vibration and noise. Vibration energy generated from a compressor's inner body is transmitted to the shell and outside through the loop pipe. For this reason it is very important to design a compressor loop pipe. But, for geometrical complexity and dynamic nonlinearity of the loop pipe, analysis and design of the loop pipe is very difficult. So the statistical and experimental methods have to be used for design of this system. The response surface method (RSM) becomes a popular meta-modeling technique f3r the complex system as this loop pipe. As starting point of loop pile's optimization, FEA model and simple experimental model are used instead of the real loop pipe model. After RS model was constructed, using sensitivity-based optimizer performed optimization for the loop pipe. And the moving least square method (MLSM) was applied to reduce the approximation error.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.4 s.316
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• pp.74-78
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• 2007

Novel concept of sensor mat and its signal processing method is proposed for patient monitoring in medical application. Proposed sensor mat structure has sensing inner layer which has cross-linked arrangement using plastic optical fiber(POF). Large core diameter of plastic optical fiber behaved as band pass filter by averaging the noise component caused by unwanted environmental factors. Signal processor followed by sensor output added noise immune performance by filtering out unwanted component. Fail-proof patient breath monitoring scheme was realized by using intelligent decision algorithm. Unlike the conventional approach by using mechanical sensor, which have high sensitivity both to signal and to environmental noise, our approach provided reliable breath motion detection.

• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.157-164
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• 2007

For a GPS antenna to normally receive GPS satellite signals during full flight mission of a satellite launch vehicle, it should be installed on skin of the vehicle. The surface of a launch vehicle is drastically heated up due to aerodynamic heating effect during flight, so that the GPS antenna mounted on surface of the launch vehicle is directly exposed to extremely hot temperature environment. Hot temperature test specification of the GPS antenna, therefore, is severer than inner components. This paper describes that procedures and results of performance analysis of the GPS antenna for KSLV-I under hot temperature environment. The GPS antenna was not deformed physically and inner LNA(Low Noise Amplifier) operated normally without performance degradation.