• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.10
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• pp.868-874
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• 2007

Noises from the helicopter rotor model are calculated numerically at various pitch angles. The aerodynamic data are calculated by using prescribed wake model and unsteady panel method. The distribution of aerodynamic loads on the blade surface are obtained from $0^{\circ}$ to $9^{\circ}$ pitch angles with equiangular increments of $1.5^{\circ}$. Although thickness noise is not related to the change of pitch angles, loading noise level increases about 3~4dBA every $1.5^{\circ}$ increment of pitch angle. The additive noise level shows sufficient value to perceive the loudness. From the result of directivity pattern the sound level at the lower region of the blade disc plane is higher than that of the upper region.

• 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.

• Speech Sciences
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• v.12 no.1
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• pp.107-119
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• 2005

The current study considers that the distinctive acoustic properties and variations in the closed plateau are realized by four different pitch accents(/Hi*_ H*/ or /Hi*_$h*_f$ for an emphatic phrase and /hi*_ H*/ for a neutral phrase) in an intermediate phrase in the French intonational structure. Thus, an attempt is made to define the acoustic property of the CP in the ip according to the duration time and pitch range, while different combinations of the four pitch accents of the CP are used to explain the way a speaker will highlight. The duration time of the CP was measured at about 0.67 sec. for males and 0.75 sec. for females. The duration properties of the plateau in the CP were found to control the pitch range based on two different prominent pitch accents, which appeared in more than two APs. Therefore, the ip was identified as having a hierarchical level in the French intonational structure, along with the AP and IP. In addition, the CP in the ip was used as a specific location to explain the pragmatic meaning of the rhythm using the two acoustic factors and different combinations of the four pitch accents.

• Phonetics and Speech Sciences
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• v.4 no.2
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• pp.21-31
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• 2012

The purpose of this study is to find the influence of Chinese falling-rising tone on the pitch pattern of corresponding partly-different-form-same-meaning Sino-Korean words delivered by Chinese learners of Korean and to examine how the falling-rising tone of corresponding Chinese words affects the pitch patterns of Sino-Korean words. The scope of this research is limited to Chinese learners of Korean, especially on two groups of Sino-Korean words - AB:CB type and AB:AC type that the are second-most frequently occuring different-form-same-meaning Sino-Korean words. In this study, Chinese learners pronounced both Chinese words and corresponding Sino-Korean words. Learners' pitch patterns were recorded and analyzed using software and compared with the tone of corresponding Chinese words. Experimental results showed that AB:CB type Sino-Korean words were not affected by Chinese 'falling-rising tone - high and level tone'. As well as AB:CB type, experimental results showed there were no significant influence on the pitch pattern of AB:AC type Sino-Korean words by Chinese falling-rising tone. But it was clear that Chinese learners' made pitch errors on both AB:CB type and AB:AC type Sino-Korean words. In conclusion, the Chinese learners' pitch patterns of partly-different-form-same-meaning Sino-Korean words are different from Korean native speakers', but their pitch errors cannot be attributed to Chinese falling-rising tone.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.940-947
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• 2009

The study aims at investigating frequency of the stuttering of stutterers according to FAF pitch alternation level, examining a stuttering group. The study has collected spoken language samples by making each 10 people of a stuttering group carry out a reading and monologue task using NAF and FAF. The results of this study were as follows. In stuttering frequency, both reading and monologue task, there was significant difference of stuttering frequency according NAF and FAF pitch alternation level. But, There was significant difference of stuttering frequency according FAF pitch alternation level. NAF levels than FAF on type of stuttering decreased at the level of all the core behavior. The decrease was a lot of block, core behavior has changed as often repeated.

• Speech Sciences
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• v.14 no.3
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• pp.77-89
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• 2007

This paper examined the intonation contours of English sentences produced by the Korean students. Thirty students participated in the speaking tasks made up of three parts: an oral interview, picture description and a conversational text reading. Their pronunciations in the parts were recorded on a minidisk. Then, two native instructors evaluated their proficiency level focusing on general intelligibility and suprasegmental aspects of the speech. Based on the results of evaluation they were divided into two groups: high and low proficiency groups. The pitch contours of three sentences produced by both the Korean students and a native speaker were compared to find any similarities and differences in the students' intonation patterns using Praat. Results showed that there was a moderate correlation in the proficiency scores of the students by the two native speakers. Secondly, students who earned high scores in the proficiency level matched better the native model. Thirdly, the high group students knew more on the pitch contour and tried to carefully realize them while fewer students in the low group answered positively on the questionnaire. In conclusion, English learners need to know the proper intonation patterns and to practice them consciously and sufficiently to realize correct intonation contours. Further studies would be desirable on the students' pronunciation focused on discourse structure.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.614-625
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• 2004

The main purpose of this study is to get flowrate coefficient 'q' and to study characteristics of flowrate of screw pump. This study is based on Muskin's formula and depends on the computer simulation. The results of study are as follows. 1. Flowrate coefficient will reduce according to increase of inclination. The larger the pitch ratio is and the smaller the diameter ratio is, the more coefficient reduces. 2. As a rule, the coefficient increases according to reduction of the diameter ratio, but the coefficient tends to reduce when the ratio is less than 0.45. So, in actual application, it is recommended that the ratio should be above 0.45. 3. If the pitch ratio increases, the coefficient increases in case of small inclination and decreases in case of large inclination. 4. The coefficient increases according to number of windings. Especially, singles winding is not used in actual application because it has too small coefficient. 5. The coefficient decreases when the influent water level falls. Flowrate is almost zero when the water level is below $40\%$ of Filling Points.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.11
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• pp.874-878
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• 2001

Solder bump was electroplated on wafer for flip chip application. The process is as follows. Ti/Cu were sputtered and thick PR was formed by several coating PR layer. Fine pitch vias were opened using via mask and then Cu stud and solder bump were electroplated. Finally solder bump was formed by reflow process. In this paper, we opened 40㎛ vias on 57㎛ thick PR layer and electroplated solder bump with 70㎛ height and 40㎛ diameter. After reflow process, we could form solder bump with 53㎛ height and 43㎛ diameter. In plating process, we improved the plating uniformity within 3% by using ring contact instead of conventional multi-point contact.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.941-945
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• 2006

In the development of electricity generating wind turbines for wind farm application, only two types have survived as the methods of power regulation; stall regulation and fun span pitch control. The sound measurement procedures of IEC 61400-11 are applied to field test and evaluation of noise emission from each of 1.5 MW and 660 kW wind turbine generators (WTG) utilizing the stall regulation and the pitch control for the power regulation, respectively. Apparent sound power level, wind speed dependence and third-octave band levels are evaluated for both of WTGs. It is found that while 1.5 MW WTG using the stall control is found to emit lower sound power than 660 kW one using the pitch control at low wind speed (below 8 m/s), sound power from the former becomes greater than that of the latter in the higher wind speed. Equivalent continuous sound pressure levels (ECSPL) of the stall control type of WTG vary more widely with wind speed than those of the pitch control type of WTG These characteristics are believed to be strongly dependent on the basic difference of the airflow around the blade between the stall regulation and the pitch control types of WTG. These characteristics according to the methods of power regulation lead to the very different noise emission characteristics of WTG depending on the seasons because the average wind speed in summer is lower than the critical velocity over which the airflow on the suction side of blade in the stall types of WT are separated. These results propose that, in view of environmental noise regulation, the developer of wind farm should give enough considerations to the choice of power regulation of their WTG based on the weather conditions of potential wind farm locations.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.9 no.1
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• pp.79-85
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• 1998

Changes in the human voice occur between infancy and old age and reflect a myriad of biological changes that influence the size, shape, and physical properties of the larynx. The human larynx is located near the base of the neck and attached inferiorly to the trachea and opens superiorly into the pharynx. The larynx by the third month of fetal life has the same features recognizable at birth. The fundamental frequency of vocal fold vibration generally becomes higher in early age, lower in middle age, and higher in old age. These decreases in Fo undoubtedly result from a combination of factors, consisting of modest increase in length and mass of the muscle and connective tissues of the vocal fold. But the level of the larynx in the neck may be closely connected with Fo directly, high larynx in related with high pitch and low larynx with low pitch. The purpose of this study is to determine the developmental level difference from child to adult larynx using conventional radiography, and the change of speaking fundamental frequency from second decade to sixth decade.