• 한국세라믹학회지
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• 제35권7호
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• pp.740-748
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• 1998

The inertia friction properties of C/C composites manufactured by the processes of pressure and at-mospheric carbonizaton with a commerciallized and two kinds of modified coal-tar pitch as a matrix pre-cursor were investigated. The modifications of a pitch such as the introduction of mesophase and the ad-dition of sulphur into a raw pitch were not effective for a impregnation efficiency conducted in a vacuum and at the same time in a pressure of 5kg/cm2 due to the increase of the pitch viscosity. There was not a difference in the densification increment between the pitch modifications however it was revealed that a pressure carbonization was more advantageous than an atmospheric in the densification and the formation of anisotropic carbon matrix. The friction and wear propertis of C/C having higher degree of matrix cry-stallization higher density and hardness of friction surface showed superiority. As the braking energy was increased the friction coefficients were decreased and reached almost same level at the high kinetic energy of 99.6kJ. The wear trends at 99.6kJ were different from the behaviors of friction ceofficient under the same energy in which an oxidation wear is being considered along with a mechnical wear although the wear rates were almost similar to the friction coefficient at the low energy.

• 한국산학기술학회논문지
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• 제13권7호
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• pp.3188-3193
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• 2012

보코더 과정 중 피치를 분석하는 과정은 코드북 분석과 더불어 부호화기 성능에 큰 영향을 미치는 부분이다. 피치를 검색하기 위해 먼저 신호의 주기성을 강조해야 하는데 일반적으로 자기상관법의 일종인 듀얼 펄스 알고리즘 기법을 이용하여 주기성을 강조한 후 피치를 검색하는 방법을 많이 사용한다. 이 방법은 한 프레임 내에서 두 개의 펄스 간격을 변경시키면서 음성신호와의 상관관계 값을 구하여 상관관계가 가장 높을 때의 펄스 간격을 찾는다. 또한 상관관계 값이 가장 높을 때의 주기가 가장 뚜렷한 반복 구간인데 이것을 피치 주기라 한다. 이때 반주기, 배주기 및 세배주기가 주된 주기로 찾아지는 경우에는 이 간격을 피치 주기라 할 수 없어 이를 해결하기 위한 여러 가지방법들이 제안되어 있다. 본 논문에서는 피치를 검색하기 전에 프레임내의 전체 에너지변화 비율을 추정하여 신호의 에너지 레벨을 미리 보상해 준 후 피치를 검색하는 방법을 제안한다. 이 방법을 적용하면 피치검색 시간을 단축할 수 있고, 피치 검색의 정확도를 높일 수 있어 전반적인 피치 검색에 관한 성능이 개선된다.

• Korea-Australia Rheology Journal
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• 제18권3호
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• pp.143-151
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• 2006

We analyzed the non-Newtonian and non-isothermal flow in a single screw extruder system and investigated the mixing performance with respect to the screw speed and the screw pitch. The viscosity of polymer melt was described with Carreau-Yasuda model. The mixing performance was computed numerically by tracking the motions of particles in the screw element system. The extent of mixing was characterized in terms of the deformation rate, the residence time distribution, and the strain. The results revealed that the high screw speed reduces the residence time but increases the deformation rate while the small screw pitch increases the residence time. It is concluded that the high screw speed increases the dispersive mixing performance and the small screw pitch increases the distributive mixing performance.

• 말소리와 음성과학
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• 제6권3호
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• pp.23-32
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• 2014

This study presents the prosodic characteristics of 'Motherese' and 'Teacherese (child care teacher and kindergarten teacher)'. 21 mothers and 24 teachers spoke to children in the child care center or kindergarten. Children are in their 4;00-6;11. Speech and articulation rate, number of accentual phrases (APs), number of intonational phrases (IPs), pitch-related factors (f0, pitch range, f0 standard deviation), and intonation slope (mean Absolute, f0, q-tone slope) were measured. 2 groups spoke 2 sentential types (interrogative_ alternative question, declarative_ coordinated sentence) in 2 situations (one accompanied with the children, the other done without children, but pretending as if they were in front of the children). The results indicate that teachers show more noticeable prosodic characteristics than mothers do.

• 설비공학논문집
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• 제14권2호
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• pp.116-126
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• 2002

A three dimensional numerical analysis of the corrugated louver fin for a vehicle heat exchanger was performed. The heat transfer rate and the air pressure drop of the corrugated louver fins for a slim heater were compared with experimental results at the same operating conditions. As for the slim heater fin, we found an optimum fin pitch at certain operating conditions. As the fin pitch increased, the air pressure drop decreased. The vertical or flat top fin was superior to the common declined fin in the aspect of heat transfer performance. As the louver length increased, both the heat transfer rate and the air pressure drop increased.

• 말소리와 음성과학
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• 제6권2호
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• pp.81-88
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• 2014

The normal aging process on speech production and these changes are perceived by listeners. This study examined whether age perception changed under various conditions of prosodic manipulations in normal listeners, comparing the prosodic changes according to age and sex in adulthood. The older and younger voices were resynthesized by manipulation of the speaking rate and pitch to shift the perceived age of the groups toward each other. Two-way repeated ANOVA were conducted to determine if the prosodic type of resynthesized cue resulted in a significant shift in perceived age of young and old voices. The manipulation of the speaking rate resulted in a significant shift in perceived age for the older and younger groups. A significant shift in age estimates was not observed for the younger male group when pitch was manipulated. There were significant gender-by-age group interactions for prosodic manipulation type. Age-related changes in the prosodic properties of speech may ultimately influence speech perception.

• 한국음향학회지
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• 제30권7호
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• pp.390-395
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• 2011

본 논문은 각 방송사의 메인 뉴스인 평일 저녁뉴스의 여성 앵커 음성 분석을 통하여 공통적인 음성 요소와 각 방송국별 상대적인 음성 및 음향에는 어떠한 차이가 있는지 연구하였다. 전반적인 음성 특성을 알아보기 위해 6가지 요소를 분석한 결과, 각 방송국별 아나운서는 발화속도를 제외하면 모든 영역에서 뚜렷한 음성 및 발성 특징을 가지고 있었으며 음향시스템적인 차이도 발견 되었다. 주요 분석 요소는 기본 피치 외에 제1포만트와 피치비율에 따른 음색과 피치대역폭을 통한 정감도 요소, 피치대역폭내의 평균피치위치를 통한 문장 끝맺음 양상, 평균 발화속도, 주파수 대역별 에너지 분포를 통한 음향적인 음색 분석이다. 분석된 수치 및 결과는 국내 여성 앵커의 발성 특징의 기준으로 참고 및 활용될 수 있다.

• Korea-Australia Rheology Journal
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• 제18권3호
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• pp.153-160
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• 2006

We analyzed the non-Newtonian and non-isothermal flow with Carreau-Yasuda viscosity model in co-rotating and counter-rotating twin screw extruder systems. The mixing performances with respect to the screw speed, the screw pitch, and the rotating direction have been investigated. The dynamics of mixing was studied numerically by tracking the motions of particles. The extent of mixing was characterized in terms of the deformation rate, the residence time distribution, and the average strain. The results showed that the high screw speed decreases the residence time but increases the deformation rate. Small screw pitch increases the residence time. It is concluded that the high screw speed increases the dispersive mixing performance, while the small screw pitch increases the distributive mixing performance. Co-rotating screw extruder has the better conveying performance and the distributive mixing performance than counter-rotating screw extruder with the same screw speed and pitch. Co-rotating screw extruder developed faster transport velocity and it is advantageous the flow characteristics to the mixing that transfers polymer melt from one barrel to the other barrel.

• 음성과학
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• 제4권2호
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• pp.69-89
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• 1998

The aim of this study is to develop an objectively method of speech evaluation for children with cleft palates. To assess velopharyngeal function, Visi-Pitch, Computerized Speech Lab. (CSL), Nasometer and Palatometer were used for this study. Acoustic parameters were measured depending on the diagnostic instruments: Pitch (Hz), sound pressure level (dB), jitter (%) and diadochokinetic rate by Visi-Pitch, VOT and vowels formant ($F_1\;&\;F_2$) by a Spectrography and the degree of hypernasality by Nasometer. In addition, Palatometer was used to find the lingual-palatal patterns of cleft palate. Ten children with cleft palates and fifty normal children participated in the experiment. The results are as follows: (1) Higher nasalance of children with cleft palates showed the resonance disorder. (2) The cleft palate showed palatal misarticulation and lateral misarticulation on the palatogram. (3) Children with cleft palates showed the phonatory and respiratory problems. The duration of sustained vowels in children with cleft palates was shorter than in the control groups. The pitch of children with cleft palates was higher than in the control groups. However, intensity, jitter and diadochokinetic rate of children with cleft palates were lower than in the control group. (4) On the Spectrogram, the VOT of children with cleft palates was longer than control group. $F_1\;&\;F_2$ were lower than in the control group.

• Korean Chemical Engineering Research
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• 제58권1호
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• pp.142-149
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• 2020

본 연구에서는 인조흑연의 낮은 이론용량을 개선하기 위하여 음극소재로서 흑연/실리콘/피치 복합소재의 전기화학적 성능을 조사하였다. 구형의 인조 흑연 표면을 polyvinylpyrrolidone (PVP) 양친성 물질로 코팅한 후 실리카를 성장시켜 흑연/실리카 소재를 합성하였으며, 석유계 피치 코팅과 마그네슘 열 환원법을 통해 흑연/실리콘/피치 복합소재를 제조하였다. 흑연/실리콘/피치 복합소재의 전극은 poly(vinylidene fluoride) (PVDF), carboxymethyl cellulose (CMC), polyacrylic acid (PAA) 바인더에 따라 제조하였으며, 다양한 전해액과 첨가제를 이용하여 전지를 조립하였다. 흑연/실리콘/피치 복합소재는 X-ray diffraction (XRD), scanning electron microscope (SEM)와 thermogravimetric analyzer (TGA)를 통해 물리적 특성을 분석하였으며, 전기화학적 특성은 충 방전 사이클, 율속, 순환전압전류, 임피던스 테스트를 통해 조사하였다. 흑연/실리콘/피치 복합소재는 흑연 : 실리카 : 피치 = 1 : 4 : 8일 때 높은 사이클 안정성을 보였다. PAA 바인더를 사용하여 제조된 전극은 높은 용량과 안정성을 보였으며, EC:DMC:EMC 전해액을 사용하였을 때 719 mAh/g의 높은 초기 용량과 우수한 사이클 안정성 나타내었다. 또한 vinylene carbonate (VC) 첨가시에 2 C/0.1 C 일 때 77% 용량 유지율과 0.1 C/0.1 C 일 때 88% 용량 회복을 나타냄을 확인하였다.