• Composites Research
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• v.14 no.4
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• pp.15-26
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• 2001

Interfacial properties and microfailure degradation mechanisms of the bioabsorbable composites fur implant materials were investigated using micromechanical technique and nondestructive acoustic emission (AE). As hydrolysis time increased, the tensile strength, the modulus and the elongation of poly(ester-amide) (PEA) and bioactive glass fibers decreased, whereas these of chitosan fiber almost did not change. Interfacial shear strength (IFSS) between bioactive glass fiber and poly-L-lactide (PLLA) was much higher than PEA or chitosan fiber/PLLA systems using dual matrix composite (DMC) specimen. The decreasing rate of IFSS was the fastest in bioactive glass fiber/PLLA composites whereas that of chitosan fiber/PLLA composites was the slowest. AE amplitude and AE energy of PEA fiber decreased gradually, and their distributions became narrower than those in the initial state with hydrolysis time. In case of bioactive glass fiber, AE amplitude and AE energy in tensile failure were much higher than in compression. In addition, AE parameters at the initial state were much higher than those after degradation under both tensile and compressive tests. In this work, interfacial properties and microfailure degradation mechanisms can be important factors to control bioabsorbable composite performance.

• Journal of the Korean Society of Safety
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• v.12 no.1
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• pp.133-139
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• 1997

The noise generated from a treadband mechanism of a tire has been the subject of this research. In particular, the treadband has been treated as an infinite tensioned beam resting on an elastic foundation which includes damping. The main objective is to predict the sound power generated from a system mentioned above by locating harmonic point forces representing the excitation of treadband at the contact patch. It is possible to predict the sound power radiated from this structure by using wavenumber transformation techniques. In order to find out the minimum radiated sound power, All parameters were varied. Thus, this model can be used as a tire design guide for selecting parameters which produces the minimum noise radiation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.896-904
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• 2017

Lean premixed combustion was successful in meeting current NOx emission regulations. However, these often leads to combustion instability. This phenomena results from the feedback relationship between heat release perturbations and acoustic pressure oscillations in the combustor. Researches on the combustion instability in an annular combustor have recently received great attention due to the enhanced NOx requirement in aero-engines. In this study, the thermoacoustic network model has been developed in order to calculate the acoustics for longitudinal as well as circumferential modes in the annular combustor. The combustion model in the network model is calculated by flame transfer function(FTF). Numerical and analytical results are compared to an measurement data.

• Proceedings of the Korea Contents Association Conference
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• 2003.11a
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• pp.23-40
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• 2003

6. ATC 성공사례 및 국내 현황 중앙대학교 AVID Training Center 1).사 업 명 AVID 미디어 공인 교육 센타 (AVID Tanning Center) 2003년 6월 서울 지역 유일하게 활동시작 2). 사 업 내 용 - 산업용 디지털 콘텐츠의 개발 - 생산 및 리 소스확보 - 디자인. 애니메이션. 영화. 게임 등 콘텐츠 제작에 필요한 다양한 디지털 이미지 음향등 산업용 콘텐츠를 산학협력에 의해 확보 - 공동활용체계 구축으로 디지털 콘텐츠 산업의 경쟁력 강화 - 디지털 콘텐츠 유통 및 전문인력 양성 콘텐츠의 국내 외 유통기반 구축 - 저작권 보호 관련기술의 표준화 지원 및 기술개발 사업지원 - 디지털 영화 제작 산업디자인, 사진, 게임, 디지털 콘텐츠의 기획 -콘텐츠 제작 관련 교육을 통한 콘텐츠 제작자의 저변 확대 - 디지털 콘텐츠 분양 정보 공동체 조성 - 디지털 콘텐츠 경영정보, 마케팅 정보의 공유 - 디지털 콘텐츠 산업 통계 및 지표 연구, 지역별 특성 연구 지원 - 디지털 콘텐츠 산업 관련 정보 네트워크 구축 제공

• The Journal of the Acoustical Society of Korea
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• v.23 no.3
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• pp.192-196
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• 2004

A decision of the modulus of elasticity is made by using the degree of bending strength of materials for loudspeaker damper and the radius of corrugation lines and the radius of curvature of each corrugation as a geometrical element. And it is compared with experimental measurements. As a result. the elasticity of damper is proportional to the degree of bending strength and inversely proportional to the radius of corrugation lines and inversely proportional to the square of the radius of curvature. We made a small loudspeaker using a modified damper which take the form of inner small curvature and outer large curvature of each corrugation. This loudspeaker have the increased sensitivity in high frequency and also in low frequency region.

• The Journal of the Acoustical Society of Korea
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• v.17 no.2
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• pp.43-49
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• 1998

본 논문에서는 고성능 CELP 음성 압축기를 위한 "Boaseline 코드벡터"와 "Implied 코드벡터"로 구성되는 새로운 구조의 코드북을 제안한다. Implied 코드벡터는 피치 주기 이 전의 합성음으로부터 구하여지며 여기(勵起)신호의 피치 구조를 강화하여 합성음의 음질을 향상시킨다. Implied 코드벡터는 전달되지 않고 인코더 및 디코더에서 각각 합성음을 이용 하여 독립적으로 구하여진다. 또한 펄스와 랜덤 성분을 모두 가지는 복합 여기방식을 이용 하여 음질을 더욱 향상시킨다. 제안된 코드북 구조를 이용하여 10msec프레임을 가지는 8kbps CELP 음성 압축기를 설계하여 하나의 DSP칩에 실시간 구현 하였고, 이것의 성능을 SNRseg와 MOS로 측정하였다. 평균 SNRseg는 12.14dB로 CS-ACELP의 SNRseg보다 6dB 높고, 조용한 환경에서의 MOS는 3.80으로 G.729 CS-ACELP의 MOS보다 0.02 높다.

• The Journal of the Acoustical Society of Korea
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• v.35 no.4
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• pp.272-279
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• 2016

In this paper, the realization of a hearing aid adaptively cancelling feedback noise was considered. Conventional least mean square method in time domain was transformed into frequency domain in order to minimize computational burden. The adaptive filter algorithm was evaluated by Matlab (Matrix laboratory), and it was confirmed by CSR 8675 Bluetooth DSP IC (Digital Signal Processor Integrated Circuit) chip firmware realization. Some remote control features by a smart phone was added to the smart hearing aid for user interface easiness.

• Journal of Ocean Engineering and Technology
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• v.16 no.2
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• pp.67-71
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• 2002

Damage process of CFRP laminates was characterized by Acoustic Emission (AE). The main objective of this study is to determine if the sources of AE in CERP laminates could be identified from the characteristics of the waveform signals recorded during monotonic tensile test. The time history and power spectrum of each individual wave signal recorded during test were examined and classified according to their special characteristics. The wave from and frequency of AE signal from a specimens is an aid to the determination of the extent of the different fracture mechanism such as matrix crack, debonding, fiber pull-out and fiber fracture as load is increased. Four distinct types of signals were observed regardless of specimen condition. The result showed that the AE method could be effectively used for analysis of fracture mechanism in CFRP laminates.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.2
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• pp.153-158
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• 2011

This paper presents subjective experimental results to understand how audio should be changed when a video clip is watched in 3D than 2D. This paper divided auditory perceptual information into two categories; distance and azimuth that a sound source contributes mostly, and spaciousness that scene or environment contribute mostly. According to the experiment for distance and azimuth, i.e. sound localization, we found that distance and azimuth of sound sources were magnified when heard with 3D than 2D video. This lead us to conclude 3D sound for localization should be designed to have more distance and azimuth than 2D sound. Also we found 3D sound are preferred to be played with not only 3D video clip but also 2D video clip. According to the experiment for spaciousness, we found people prefer sound with more reverberation when they watch 3D video clips than 2D video clips. This can be understood that 3D video provides more spacial information than 2D video. Those subjective experimental results can help audio engineer familiar with 2D audio to create 3D audio, and be fundamental information of future research to make 2D to 3D audio conversion system. Furthermore when designing 3D broadcasting system with limited bandwidth and with 2D TV supportive, we propose to consider transmitting stereoscopic video, audio with enhanced localization, and metadata for TV sets to generate reverberation for spaciousness.

• Journal of Ocean Engineering and Technology
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• v.16 no.4
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• pp.48-53
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• 2002

Fiber-reinforced composites are extensively used in electronic, ship and aerospace applications due to their high strength and high toughess. In these applications, they are often subjected to localized heat damage due to various sources. In order to ensure their reliability, it is important to predict their residual properties using nondestructive evaluation thchniques. Fabric fiber composite specimens were manufactured with six layers of the glass-fiber prepreg and the carbon-fiber prepreg, respectively. The specimens were subjected to a localized heat damage using a heated copper tip with a diameter of 10mm at 35$0^{\circ}C$(CFRP) and 30$0^{\circ}C$(GFRP), respectively. The specimens were then subjected to tension tests while acoustic emission (AE) activities of specimens were collected. The AE activity of all specimens showed three types of distinct frequency regions. Those are matrix cracking, failure of the fiber/matrix interface and fiber breakage.