• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2511-2514
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• 2008

As the minimum feature size decreases, techniques to avoid contamination and processes to maintain clean wafer surfaces have become very important. The deposition and detachment of nanoparticles from surfaces are major problem to integrated circuit fabrication. Therefore, cleaning technology which reduces nanoparticles is essential to increase yield. Previous megasonic cleaning technology has reached the limits to reduce nanoparticles. Megasonic cleaning is one of the efficiency method to reduce contamination nanoparticle. Two major mechanisms are active in a megasonic cleaning, namely, acoustic streaming and cavitation. Acoustic streaming does not lead to sufficiently strong force to cause damage to the substrates or patterns. Sonoluminescence is a phenomenon of light emission associated with the cavitation of a bubble under ultrasound. We studied a correlation between sonoluminescence and sound pressure distribution for the minimum of pattern damage in megasonic cleaning.

• Advances in aircraft and spacecraft science
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• v.3 no.3
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• pp.331-349
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• 2016

Stiff and light fibre reinforced composites as used in air- and space-craft applications tend to high sound emission. Therefore, the damping properties are essential for the entire structural and acoustic engineering. Viscous damping is an established and reasonably linear model of the dissipation behaviour. Commonly, it is assumed to be isotropic and constant over all modes. For anisotropic materials it depends on the fibre orientation as well as the elastic and thermal material properties. To portray the orthogonal anisotropic behaviour, a model for unidirectional fibre reinforced plastics (frp) has been developed based on the classical laminate theory by ADAMS and BACON starting in 1973. Their approach includes three damping coefficients - for longitudinal damping in fibre direction, damping transversal to the fibres and shear based dissipation. The damping of a laminate is then accumulated layer wise including the anisotropic stiffness. So far, the model has been applied mainly to thermoset matrix materials. In this study, an experimental parameter estimation for different thermoplastic frp with angle ply and cross ply layups was carried out by measuring free vibrations of cantilever beams. The results show potential and limits of the ADAMS/BACON damping criterion. In addition, a possibility of modelling the anisotropic damping is shown. The implementation in standard FEA software is used to study the influence of boundary conditions on the damping properties and numerically estimate the radiated sound power of thin-walled frp parts.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3458-3463
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• 2007

Leakage would happen because of the damage of high temperature and high-pressure valve in nuclear power plant. condition based prevention maintenance is essential by using the suitable method based on local condition. Energy loss prevention can prevent from an accurate test, Local actually and ability. The methods of test for high energy fluid leakage at present are analysis of ${\Delta}$T, AE(Acoustic Emission) analysis, and thermal image. The result for test of AC (Main steam) system in YNG 2 Unit reveals that the AE occurred clearly in leakage situation, but thermal image didn't occur. It is identified that leakage is occurred when the orifice located front and back of valve operates. It shows that making a impatient judgment by using the single method if it is leakage is containing uncertainty. So I think that using the Multi-Measuring method is more sound judgment than Single-Measuring method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.9
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• pp.1284-1291
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• 2002

Combustion instabilities are an important concern associated with lean premixed combustion. Laboratory-scale dump combustor was used to understand the underlying mechanisms causing combustion instabilities. Experiments were conducted at atmospheric pressure and sound level meter was used to track the pressure fluctuations inside the combustor. Instability maps and phase-resolved OH chemiluminescence images were obtained at several conditions to investigate the mechanism of combustion instability and relations between pressure wave and heat release rate. It showed that combustion instability was susceptible to occur at higher value of equivalence ratio (>0.6) as the mean velocity was decreased. Instabilities exhibited a longitudinal mode with a dominant frequency of ∼341.8 Hz, which corresponded to a quarter wave mode of combustor. Heat release and pressure waves were in-phase when instabilities occurred. Rayleigh index distribution gave a hint about the location where the strong coherence of pressure and heat release existed. These results also give an insight to the control scheme of combustion instabilities. Emission test revealed that NOx emissions were affected by not only equivalence ratio but also combustion instability.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1482-1489
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• 2007

In this paper, characteristics of infrasound and low-frequency noise emission from large modern wind turbines are experimentally investigated. The sound measurement procedures of IEC 61400-11 and ISO 7196 are utilized to field test and evaluation of noise emission from each of 1.5 MW and 660 kW wind turbines using the stall regulation and the pitch control for the power regulation, respectively. It was found that the G-weighted SPLs of low-frequency noise including infrasound shows positive correlation with the wind speeds, irrespective of methods of power regulation. This highlights the potential complaint of local community against the infrasound and low-frequency noise of wind turbines. The comparison of measured data with the existing hearing thresholds and criteria curves shows that it is highly probable that the low-frequency noise from the 1.5 MW and 660 kW wind turbines in the frequency range over 30 Hz leads to the psychological complaint of ordinary adults, and that the infrasound in the frequency range from 5 Hz to 8 Hz causes the complaint by rattling the house fitting such as doors and windows.

• Journal of Power System Engineering
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• v.11 no.3
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• pp.35-40
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• 2007

Leak would happen because of the damage of high temperature and high-pressure valve in nuclear power plant. condition based prevention maintenance is essential by using the suitable method based on local condition. Energy loss prevention can prevent from an accurate test, Local actually and ability. The methods of test for high energy fluid leak at present are analysis of ${\Delta}T$, AE(Acoustic Emission) analysis, and thermal image. The result for test of secondary system in nuclear power plant Unit reveals that the AE occurred clearly in leakage situation, but thermal image didn't occur. It is identified that leak is occurred when the orifice located front and back of valve operates. It shows that making a impatient judgment by using the single method if it is leakage is containing uncertainty. So we think that using the Multi-Measuring method is more sound judgment than single-measuring method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.985-990
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• 2004

Leak noise is a good source to identify the exact location of a leak point of underground water pipelines. Water leak generates broadband noise from a leak location and can be propagated to both directions of water pipes. This sound propagation due to leak in water pipelines is not a non-dispersive wave any more because of the surrounding pipes and soil. However, the necessity of long-range detection of this leak location makes to identify low-frequency acoustic waves rather than high frequency ones. Acoustic wave propagation coupled with surrounding boundaries including cast iron pipes is theoretically analyzed and the wave velocity was confirmed with experiment. The leak locations were identified both by the acoustic emission (AE) method and the cross-correlation method. In a short-range distance, both the AE method and cross-correlation method are effective to detect leak position. However, the detection for a long-range distance required a lower frequency range accelerometers only because higher frequency waves were attenuated very quickly with the increase of propagation paths. Two algorithms for the cross-correlation function were suggested, and a long-range detection has been achieved at real underground water pipelines longer than 300m.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.638-643
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• 2011

The aluminum soundproofing panel used to the traffic noise reduction will judge with the material to improve because the CO2 emission is greater than other soundproofing panel such as plastic soundproofing panel. Also, if the air-passing soundproofing panel which can endure the fast wind velocity will be developed, it judged that it can reached to the target of low CO2 traffic technology development using the reduction of material cost and the lower consumption of steel. The objective of this study is to improve the soundproofing panel and to develop the air-passing soundproofing panel for the replacement of aluminum sound proofing panel which is more emit CO2 than other soundproofing panel. And, we tried to develop the reduction technology of CO2 emission through the development of air-passing soundproofing panel. At first, the flow and noise simulation were conducted for the purpose of the calculation of wind pressure on soundproofing wall and noise exposure level on receiver points according to the open ratio of air-passing soundproofing panel. And the 1st and 2nd mockup of air-passing soundproofing panel were made, and the design load test were conducted for these mockup.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.4
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• pp.954-967
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• 1996

Laser application to modify healthy permanent dentin to improve microhardness and caries resistence has been previously reported but the physical modification and ablation thresholds of carious and sclerotic dentin has yet to be identified. This study determined the energy density required by modify (physical modification threshold, PMT) and remove (ablation threshold, AT) infected carious, affected and selerotic dentin compared to healthy permanent dentin. $1{\pm}0.25mm$ thick dentin sections(n=272) from extracted human teeth were used. Smear layer was removed 0.5M EDTA for 2 minutes. Utilizing three pulsed fiberopitc delivered contact lasers with different emission wavelengths($1.06{\mu}m$=Nd : YAG, $2.10{\mu}m$=Ho : YAG and $2.94{\mu}mEr$ : YAG). The energy density($J/cm^2$) was incrementally increased and the resulting tissue interaction classified on a scale from 0-6. A minimum of 5 repetitions/energy density were completed. Light microscopy(10-25X) was used to verify the physical modification(scale=3) and ablation thresholds(scale=4) of the various forms of dentin and the data were analyzed by logistic regression at the 95 % confidence interval. PMT and AT by the laser and the dentin types were: PMT and AT was lower in infected dentin than in sound dentin for all lasers. PMT and AT induced by Nd : YAG>Ho : YAG>Er : YAG for all forms of dentin. Microhardness was increased in sound dentin at PMT. Morphology of crater examined by light microscopy showed Nd : YAG was safe and effective for removing carious dentin and Er: YAG was effective for removing sound dentin. The PMT and AT for YAG lasers are different as a function of dentin type which may be utilized for selective modification and removal of dentin.

• Journal of the Institute of Convergence Signal Processing
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• v.21 no.3
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• pp.121-126
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• 2020

Sound-based machine fault diagnosis is the automatic detection of abnormal sound in the acoustic emission signals of the machines. Conventional methods of using mathematical models were difficult to diagnose machine failure due to the complexity of the industry machinery system and the existence of nonlinear factors such as noises. Therefore, we want to solve the problem of machine fault diagnosis as a deep learning-based image classification problem. In the paper, we propose a CNN-based automatic machine fault diagnosis method using Spectrogram images. The proposed method uses STFT to effectively extract feature vectors from frequencies generated by machine defects, and the feature vectors detected by STFT were converted into spectrogram images and classified by CNN by machine status. The results show that the proposed method can be effectively used not only to detect defects but also to various automatic diagnosis system based on sound.