• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.5
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• pp.219-225
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• 2003

This paper described about the acoustic wave measurement method to diagnose GIS for particles. We measured and analyzed the signals of acoustic waves with two type acoustic sensors having 125kHz and 50kHz resonant frequency respectively when the particles were bounced on the inside surfaces of GIS tanks by the electrostatic force. To use two sensors for the diagnosis of GIS, we set up the calibration method for this measurement method. We showed the output characteristics of two sensors according to the sizes and materials of particles in the experiment. As the results, the inception voltages bouncing particles depended on the materials and the extinction voltages bouncing them depended on the sizes and materials. We found out that the relationship between sizes of particles and output voltages of sensors didn't have linearity but the ratios of between peak values of two sensors depended on the materials of GIS enclosures and the sizes of particles.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.6
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• pp.246-252
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• 2002

This paper describes the acoustic emission measurement method to diagnose GIS for particles. We measured and analyzed the signals of acoustic waves using acoustic two types sensors with 125KHz and 50KHz resonant frequency respectively when the particles were dropped on the surfaces of circular plates and inside of GlS tanks. We found that the difference between peak outputs of two sensors depended on the types and materials of particles and the conditions of dropping position. These results showed that the outputs of 125KHz sensor were higher than those of 50KHz sensor in circular plate and 362㎸ GIS tank made of steel and vice versa in circular plate and 800㎸ GIS tank made of aluminum. The ratios outputs of 125KHz sensor to those of 50KHz sensor were 1.4 - 2.37 in 800㎸ GIS tank and were 0.5 - 1.0 in 362㎸ GIS tank. Therefore we knew that adaption of two types acoustic sensors which had different resonant frequencies as a very useful method in diagnosis of GIS.

• Restorative Dentistry and Endodontics
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• v.17 no.1
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• pp.153-165
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• 1992

Dental composite resin is a kind of the particle - reinforced composite material, and is widely used in recent dental restoration of anterior and posterior tooth region. The purpose of this study was to investigate the fracture behaviour according to volume fractions and external findings of the filler particles for better interpretation of the fracture characteristics of posterior dental composite resins by analytic method of fracture mechanics. The plane strain fracture toughness($K_{IC}$) and Acoustic Emission were determined with three - point bending test using the single edge notch specimen according to the ASTM - E399, and its analyzed data was compared with filler volume fractions derived from the standard ashing test and scanning electron fractographs of each specimen including the unfilled experimental resin as a control. The results were that the value of fracture toughness of the composite resin material was in the range from 0.85 MPa$\sqrt{m}$ to 1.60 MPa$\sqrt{m}$ and was higher than the value of the unfilled experimental resin, and the fracture behaviours dervied from Acoustic Emission analysis show prominent differences according to the volume fraction and the size of filler particles used in each composite resin. The degree of resistance against crack propagation seems to be increase and the fractographs demonstrate the high degree of surface roughness and irregularity according with the increase of fracture toughness value.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.5
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• pp.219-219
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• 2003

This paper described about the acoustic wave measurement method to diagnose GIS for particles. We measured and analyzed the signals of acoustic waves with two type acoustic sensors having 125kHz and 50kHz resonant frequency respectively when the particles were bounced on the inside surfaces of GIS tanks by the electrostatic force. To use two sensors for the diagnosis of GIS, we set up the calibration method for this measurement method. We showed the output characteristics of two sensors according to the sizes and materials of particles in the experiment. As the results, the inception voltages bouncing particles depended on the materials and the extinction voltages bouncing them depended on the sizes and materials. We found out that the relationship between sizes of particles and output voltages of sensors didn′t have linearity but the ratios of between peak values of two sensors depended on the materials of GIS enclosures and the sizes of particles.

• Phonetics and Speech Sciences
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• v.14 no.2
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• pp.11-17
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• 2022

English vowels play an important role in verbal communication. However, Korean students tend to experience difficulty pronouncing a certain set of vowels despite extensive education in English. The aim of this study is to apply speech recognition software to evaluate Korean students' pronunciation of English vowels in minimal pair words and then to examine acoustic characteristics of the pairs in order to check their pronunciation problems. Thirty female Korean college students participated in the recording. Speech recognition rates were obtained to examine which English vowels were correctly pronounced. To compare and verify the recognition results, such acoustic analyses as the first and second formant trajectories and durations were also collected using Praat. The results showed an overall recognition rate of 54.7%. Some students incorrectly switched the tense and lax counterparts and produced the same vowel sounds for qualitatively different English vowels. From the acoustic analyses of the vowel formant trajectories, some of these vowel pairs were almost overlapped or exhibited slight acoustic differences at the majority of the measurement points. On the other hand, statistical analyses on the first formant trajectories of the three vowel pairs revealed significant differences throughout the measurement points, a finding that requires further investigation. Durational comparisons revealed a consistent pattern among the vowel pairs. The author concludes that speech recognition and analysis software can be useful to diagnose pronunciation problems of English-language learners.

• The Journal of the Acoustical Society of Korea
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• v.26 no.7
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• pp.317-322
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• 2007

This paper is the first step to study on the acoustic characteristics of the Haegeum, a Korean traditional bowed-string instrument. We measured acoustic transfer functions of a Haegeum body using impulse response method. All the measurements are performed in anechoic chamber, INMC, SNU. We examined resonant characteristics of the Haegeum body with obtained transfer functions. Then we performed additional studies which are the Chladni pattern experiments and calculations of air cavity resonances to verify relations between the resonant peaks on the transfer functions and the resonances of each component, such as top plate, air cavity and so on. As a result, we can explain the acoustic characteristics of a Haegeum body and its components.

• Advances in Computational Design
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• v.8 no.4
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• pp.273-293
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• 2023

This study evaluated the acoustic performance of two configurations of serial HR arrays and lined HR arrays in the presence of grazing flow using a 3D numerical simulation. The dual, triple, and quad HR arrays were compared to the conventional HR array. The simulation results showed that the number of resonant frequencies increased with the number of serial HR arrays. The C_TL did not significantly change with the number of serial HR arrays. The acoustic performance of the two, three, and four-lined HR arrays was compared to the conventional HR array. The results showed that the resonant frequency and TLmax increased with the number of lined HR arrays. The C_TL also increased with the number of lined HR arrays. The effect of the grazing flow Mach number (M_a) was investigated on the four-lined HR array configuration and compared to the conventional HR configuration. TLmax and C_TL decreased for both configurations with increasing M_a. The four-lined HR array configuration had significantly better acoustic performance than the conventional HR configuration. The TLmax and C_TL increased by more than 300% when the configuration was changed from the conventional HR to the four-lined HR array at M_a = 0.The increment percentage decreased with increasing M_a.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.183-186
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• 2001

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.177-178
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• 2011

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.407-408
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• 2010