• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.283-288
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• 2003

The object of this study is to investigate a fracture characteristics of static tensile test as a function of acoustic emission according to the fiber orientation $\theta=0^{\circ}C$ in carbon/epoxy composites, CFRP. On tensile loading, it was recognized that the fracture characteristics of CFRP in a unidirectional composites. Using the results of the AE analysis(a=2mm), it was found that the amplitude distributions of AE signals corresponding the matrix cracking, fiber debonding or delamination, and fiber breaking are 55~70dB(<200sec), 100dB(200~600sec), and 80dB(>600sec).

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.289-294
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• 2003

The object of this study is to investigate the effect of compounded welding by using acoustic emission (AE) signals fur weld heat affected zone (HAZ) in tensile testing. This study was carried out a SM 490A high tension steel for electronic shielded metal are welding (SMAW), $\textrm{CO}_2$ gas arc welding and TIG welding. And correspondingly, the root openings are 3, 4 and 2.8mm. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. These history plots give us useful and powerful information to analyze the results of material evaluation testing.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.307-312
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• 2003

The object of this study is to investigate a damage estimation of single edge cracked tensile specimens ($2_a$/W) as a function of acoustic emission (AE) according to the unidirectionally oriented carbon/epoxy composites, CFRP AE signals were analyzed and classified 3 regions by event counts, energy and amplitude for coressponding applied load. On tensile loading and using the results of the AE analysis, it was found that the event counts, cumulative counts or energy, and amplitude distributions useful for the prediction of damage failure.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.245-248
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• 1997

The distilled water is used for the ultrasonic wave propagating material in the measurements of broadband ultrasonic attenuation (BUA) that is applied in industrial and medical applications, The acoustic impedance of water is significantly changed with its temperature. Therefore, the quantitative evaluation of BUA with temperature and the ultrasonic wave propagating distance is highly needed. In this study, we evaluated the variation of attenuation with change in temperature. To measure the variation of BUA in the low frequency region at the temperatures, 27$^{\circ}C$, 29$^{\circ}C$, and 31$^{\circ}C$, we tested the Plyethylene, Teflon, MC-Nylon, Urethane specimens and analyzed the center frequency, frequency bandwidth, spectral peak amplitude. The results showed that BUA value appeared to be lower with increasing temperature. This may be due to the fact that the frequency feature of ultrasonic wave is affected by not only the specific gravity, acoustic impedence, but material crystalline, porosity, the distance of ultrasonic wave propagation in water.

• Proceedings of the KSPS conference
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• 2007.05a
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• pp.176-179
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• 2007

This study examined the acoustic characteristics in women diver's Soombijil sound. A total of 18 women divers was attended this study. Acoustic analysis was performed via Praat. Soombijil sound were classified into three types as pitch variations in beginning, middle, and ending part. Type I showed increasing-decreasing-flat. Type II was identified by the shape of flat-flat-increasing. The shape of type III showed increasing-decreasing-increasing. Duration of Soombijil sound was mean 1.48 sec. The range of frequency was 1591.54 ${\sim}$ 4477.13 Hz. FFT analysis showed that frequencies were concentrated 500${\sim}$2000 Hz. Type I and II showed two peaks at 500 Hz and 1500${\sim}$2000 Hz. Type III has one peak below 500 Hz.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.363-370
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• 2003

The object of this study is to investigate the effect of compounded welding by using an acoustic emission (AE) signals and doing a source location for weld heat affected zone (HAZ) through tensile testing. This study was carried out a SM 490A high tension steel for electronic shielded metal arc welding (SMAW), $CO_2$ gas arc welding and TIG welding. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. These history plots are displays showing the chronological course of the test. Also, source location gives the X- and Y-coordinates of the AE source.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.10 s.103
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• pp.1211-1216
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• 2005

Underwater acoustic transducers are widely used for SONAR application, whose important design parameters are shapes. materials, dimensions and supporting structures. Practical design method of transducers consists of manufacturing, experiments and modifications so that it requires much time and expenses. In this study, an analytical method was developed for the Tonpilz type transducers using the commercial finite element analysis code ATILA which can solve the electro-mechanical coupling problems. A finite element model was established including the transducer elements such as ceramic stack, head mass, tail mass, tensile bolt, and molding layers. The proposed model was verified and modified by comparing the in-air and in-water test results of prototypes. The developed analysis method will be effectively used for the sensitivity analysis of design parameters in transducer design process.

• Proceedings of the KSPS conference
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• 2006.05a
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• pp.101-104
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• 2006

The present study examined two acoustic characteristics(duration and intensity) of vowels produced by 4 cerebral palsic adults and 4 nondisabled adults in conversational and clear speech. In this study, clear speech means: (1) slow one's speech rate just a little, (2) articulate all phonemes accurately and increase vocal volume. Speech material included 10 bisyllabic real words in the frame sentences. Temporal-acoustic analysis showed that vowels produced by two speaker groups in clear speech(in this case, more accurate and louder speech) were significantly longer than vowels in conversational speech. In addition, intensity of vowels produced by cerebral palsic speakers in clear speech(in this case, more accurate and louder speech) was higher than in conversational speech.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.278-284
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• 1998

In order to measure the real contact force between head and disk on hard disk drive quantitatively, many technique of measurement have been developed. Acoustic Emission Sensor can be used for detect elastic energy of head/disk contact as arms value. In this study using pencil breaking test is proposed for finding contact force using transfer function between calibrated force and real contact force. And real AE data of subambient and tripad slider shows bending and torsional mode and their energy are dominant in hard disk and head contact.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2004.11a
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• pp.343-348
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• 2004

Since its foundation of Won-Buddhism in 1916 there established around 500 Temple-Halls in both domestic and overseas areas, and it is a native religion that currently on its development of edification activities. As for Won-Buddhism which being under rapid development likely as such going, together with its expansion of the religious influence, there required more broader spaced grand sanctum at where the large-scaled religious events are able to perform. According to this, Balcony-styled plane form is on increasing trend from the internal plane form of Won Buddhism Sanctum. On such viewpoint, this study hereby intends to grasp the character of room acoustics through on-the-spot survey about the objects of 3 Won Buddhism Sanctums which equipped with mutually different characters of the balconies already built, and willing to furnish the fundamental material which enables to improve acoustic capability when design Won Buddhism Sanctum equipped with balcony in the future.