• Journal of the Korean Ceramic Society
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• v.35 no.7
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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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.7
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• pp.3188-3193
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• 2012

It is important to search a pitch for vocoder. The major drawback to vocoders is their large computational requirements in searching a pitch and a codebook. In this paper, a simple method is proposed to improve the pitch searching process in the pitch filter almost without degradation of quality. The period of speech signal is emphasized by using Dual Pulse technique, the same type of autocorrelation method, in pitch search. Sometimes the incorrect pitch can be obtained by halving, doubling and trifling, To solve it, before searching a pitch, we estimate energy rate in a frame and compensate envelop of signal with it. By using the proposed algorithm in pitch search, its required computation are reduced and searching pitch is improved.

• Korea-Australia Rheology Journal
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• v.18 no.3
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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.

• Phonetics and Speech Sciences
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• v.6 no.3
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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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.2
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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.

• Phonetics and Speech Sciences
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• v.6 no.2
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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.

• The Journal of the Acoustical Society of Korea
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• v.30 no.7
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• pp.390-395
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• 2011

This paper covers the studies on common voice parameters through the voice analysis of female main news anchors on weekday evening by the station, and differences of relative voices and sounds among stations. To examine voice characteristics, 6 voice parameters were analyzed and it showed anchors of each station had distinctive characteristics of voices and phonations over all fields except the speech rate, and there were also differences in sound systems. As major analysis parameters, basic pitch, tone of the 1st formant and pitch ratio, level of closeness by pitch bandwidth, type of sentence closing through average pitch position within pitch bandwidth, average speech rate, and acoustic tone analysis by energy distribution by frequency band were used. Analyzed values and results could be referred to and utilized in the criteria of phonation characteristics for domestic female news anchors.

• Korea-Australia Rheology Journal
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• v.18 no.3
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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.

• Speech Sciences
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• v.4 no.2
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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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• v.58 no.1
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• pp.142-149
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• 2020

In this study, the electrochemical performance of Graphite/Silicon/Pitch composites as anode material was investigated to improve the low theoretical capacity of artificial graphite. Spherical artificial graphite surface was coated with polyvinylpyrrolidone (PVP) amphiphiles material to synthesize Graphite/Silica material by silica islands growth. The Graphite/Silicon/Pitch composites were prepared by petroleum pitch coating and magnesiothermic reduction. The Graphite/Silicon/Pitch composite electrodes manufactured using poly(vinylidene fluoride) (PVDF), carboxymethyl cellulose (CMC) and polyacrylic acid (PAA) binders. The coin type half cell was assembled using various electrolytes and additives. The Graphite/Silicon/Pitch composites were analysed by X-ray diffraction (XRD), scanning electron microscope (SEM) and a thermogravimetric analyzer (TGA). The electrochemical characteristics of Graphite/Silicon/Pitch composite were investigated by constant current charge/discharge, rate performance, cyclic voltammetry and electrochemical impedance spectroscopy. The Graphite/Silicon/Pitch composites showed high cycle stability at a graphite/silica/pitch ratio (1:4:8 wt%). When the electrode is prepared using PAA binder, the high capacity and stability is obtained. The coin type half cell assembled using EC: DMC: EMC electrolyte showed high initial capacity (719 mAh/g) and excellent cycle stability. The rate performance has an capacity retention (77%) at 2 C/0.1 C and an capacity recovery (88%) at 0.1 C / 0.1 C when the vinylene carbonate (VC) was added.