• 말소리와 음성과학
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• 제15권1호
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• pp.9-17
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• 2023

이 연구의 목적은 한국어 이중모음 /ㅛ/가 다양한 언어학적 환경에서 어떠한 발음 변이 양상을 보이는지 밝히는 것이다. 특히 음성적 변이와 분포 범위의 연관성에 주목하여 /ㅛ/의 발음 양상을 논의하였다. 서울코퍼스의 여성 화자 10명의 발화에서 나타난 /ㅛ/의 운율적 위치(단음절, 어절 초, 어절 중, 어절 말)와 어휘 부류(내용어, 기능어)를 분석하였다. 각 환경에서 /ㅛ/의 출현 빈도를 파악한 결과, 운율적 위치에 따라 어휘 부류와 발음형 실현이 달라지는 양상을 보였다. 음향 분석을 통해 기능어에서 나타나는 /ㅛ/에서는 음성적 약화가 빈번하게 일어나는 것을 확인하였다. 어휘 부류는 /ㅛ/의 평균적인 음가를 달라지게 하지는 않았지만 개별 토큰의 분포 양상에서는 차이가 발견되었다. 이를 통해 언어학적 환경이 모음의 음성적 분포 양상에 영향을 미친다는 것을 알 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.289-294
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• 2002

In this study, performance, flow characteristics and noise of a cross-flow-fan system, used in indoor unit of the split-type air conditioner, were predicted by computational simulation. Triangular elements were used to mesh the calculation domain and quadrilateral elements were attached to the blade surfaces and walls to enhance the simulation quality. The unsteady incompressible Wavier-Stokes equations were solved using a sliding mesh technique on the interface between rotating fan region and the outside. Two stripes of velocity stream inside the cross-flow-fan were shown - the one was due to the eccentric vortex and the other was due to the normal entrance flow. As the flow rate increased, the center of the eccentric vortex moved toward the inner blade tip and rear-guide, and the exiting flow still had velocity variation along the stabilizer, which can increase the noise level. The acoustic pressure was calculated by using Lowson's equation. From the calculated acoustic pressure, it was found that the trailing edge is a dominant of acoustic generation.

• 센서학회지
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• 제28권6호
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• pp.371-376
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• 2019

We have developed an acoustic resonance inspection system to inspect the welding defects in the mechanical parts fabricated using friction stir welding method. The inspection system was consisted of a DAQ board, a microphone sensor, an impact hammer, and controlled by a PC software. The system was developed to collect and analyze the sound signal generated by hitting the sample with an impact hammer to determine whether it is defective. In this study, 100% welded good samples were compared with 95%, 90%, and 85% welded samples, respectively. The variation of the completeness in welding did not affect the visual appearance in the samples. As a result of analyzing the natural frequencies of the good samples, the five natural frequency peaks were identified. In the case of the defective samples, the frequency change was observed. The welding failure detection time was fast enough to be only 0.7 seconds. Employing our welding defect inspection system to the actual industrial field will maximize the efficiency of quality inspection and thus improve the productivity.

• 한국환경과학회지
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• 제18권11호
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• pp.1299-1307
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• 2009

In order to measure in-situ suspended particle size, volume concentration of suspended particulate matter and current speed, mooring observation was performed at the Gwangyang Bay by using of an optical instrument, 'LISST-100' and an acoustic instrument, 'ADV'(St. S1). And the sediment flux was obtained based on the concentration of suspended particulate matter and current speeds measured at three lines of Gwangyang Bay during ebb and flood tide of August 2006. To investigate the spatial variation of suspended particulate matter, profiling observations were measured difference echo intensity and beam attenuation coefficient by using of ADCP and Transmissometer (Line A, B, C). The suspended sediment flux rate at the mouth of Gwangyang Bay was observed to be higher during asymmetrical than symmetrical of current speeds. The flux of suspended particulate matter concentration and current speeds were transported to southeastern direction of surface layer and northwestern direction of bottom layer at the western area at line A of Gwangyang Bay. Small suspended particles have been found to increase attenuation and transmission more efficiently than similar large particles using acoustic intensity (ADV/ADCP) or optical transmit coefficient (LISST-100/Transmissometer). The application and problems as using optical or acoustic instruments will be detected for use in time varying calibrations to account for non-negligible changes in complex environments in situ particle dynamics are poorly understood.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.772-777
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• 2006

An acoustic finite element model of a bridge is developed to evaluate the noise generated by the traffic-induced vibration of the bridge. The dynamic response of a multi-girder bridge, modeled by a 3-dimensional frame element model, is analyzed with a 3-axle(8DOF) truck model and a 5-axle(l3DOF) semi-trailer. The flat plate element is used to analyze the acoustic pressure due to the fluid-structure interactions between the vibrating surface and contiguous acoustic fluid medium. The radiation fields of noise with a specified distribution of vibrating velocity and pressure on the structural surface are also computed using the Kirchhoff-Helmholtz integral. In an attempt to illustrate the influence of the structural vibration noise of a bridge to total noise level around the bridge, the random function is used to generate the vehicle noise source including the engine noise and the rolling noise interacting between the road and tire. Among the diverse parameters affecting the dynamic response of bridge, the vehicle velocity, the vehicle weight, the spatial distribution of the road surface roughness, the stiffness degradation of the bridge and the variation of the air temperature changing the air density are found to be the main factors that increase the level of vibration noise. Consequently, The amplification rate of noise increases with the traveling speed and the vehicle weight.

• 전기학회논문지
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• 제57권7호
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• pp.1187-1194
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• 2008

This paper presents a high-power electronic ballast for a metal-hallide lamp(MHL) that employs frequency modulation(FM) technique to eliminate acoustic resonance(AR). The proposed ballast consists of a full-bridge rectifier, a power factor correction(PFC) circuit, a full-bridge(FB) inverter, an ignitor using LC resonance and an FM control circuit. Whereas a manual PFC provides advantages in terms of high reliability and low cost for constructing the circuit, it is difficult to supply a stable voltage because of the output voltage ripple that occurs with a period of 120Hz. Although the ballast can be designed with a small size and a light weight if it is driven at a switching frequency between 1 and 100 kHz, AR will occur if the eigen-value frequency of the lamp coincides with the inverter's operation frequency. The operation frequency was modulated in real time according to the output voltage ripple to compensate for the variation in power supplied to the lamp and eliminate AR. Performance of the proposed technique was validated through numerical analysis, computer simulation using PSPICE and by applying it to an electronic ballast for a prototype 1kW MHL.

• 전기학회논문지
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• 제57권7호
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• pp.1175-1180
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• 2008

Recently agriculture has been intelligenced and automatized because the number of agricultural population is reduced, and the various agricultural machine is developed and utilized actively, In these agricultural automation system, the solenoid valve is widely used for the supply of water and fertilizer to the plant and soil. In this solenoid valve system, AC excitation solenoid valve is widely used because of economic merit and simple system scheme. However, the instantaneous chattering vibration and noise of plunger caused by the alternative MMF variation is very important performance characteristics. In order to reduce vibration the DC excitation solenoid valve is sometimes applied for the high-end applications. In this case, the control circuit is essential to control DC excitation current. It may causes the cost increase and system complexity and it is not suitable for the outdoor agricultural machine. In this paper, the electromagnetic structural improvement of AC solenoid valve is studied to reduce the dynamic vibration and noise. As an economical solution, the shading coil is additionally implemented to the conventional solenoid valve. As a result of this study, the vibration and acoustic noise is largely reduced by the compensating MMF of shading coil and it is verified by the test of prototype.

• 대한후두음성언어의학회지
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• 제9권1호
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• pp.53-58
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• 1998

Objectives : To compare the voice quality and voice problems of untrained professional voice user groups with that of normal control group without voice problem. Materials and Methods : The sustained vowel sounds of 13 male and 36 female teachers, 46 clergies and 15 telephone operators, and 40 normal male and 20 normal female persons were analyzed, using a videostroboscopy and acoustic analyzer. Together with these analyses, a questionnaire associated with risk factors for current and past voice problems was handed over to the patients. Results : The most common symptom in subjective groups was the voice fatigue. In stroboscopic examination, the professional voice user groups shelved functional voice disorder findings regardless of the Intensity of voice use. In the clergy and teacher using loud voice, vocal polyp, vocal nodule and hyperfunction of laryngeal muscle were frequently observed. In the clergy and telephone operator, jitter and shimmer were significantly increased. In the female teacher, the value of jitter, fundamental frequency variation and fundamental frequency were statiscally significant. However, the voice of male teacher showed no significant findings in the acoustic and aerodynamic studies. Conclusion : In the management of voice problems for untrained professional voice user groups, it is important to find the exact causes and patterns of voice problems, and to be individualized the management according to the causes.

• 대한의용생체공학회:의공학회지
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• 제13권3호
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• pp.195-200
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• 1992

This paper deal with the acoustic cues of Pyoung-An Do dialect using linear prediction. Also, this paper descrbes a statistical comparison between standard tone speech data and Pyoung-An Do dia lects. The analysis done mainly focused on the distribution of formants and pitch periods accord to ac- cents variation. For the purpose of objective comparison, the experiments are performed by extracts for- mant LPC spectrum and pithch periods from average magnitude difference function waveforms. Summing up the results, In disyllable words (VCV pattern) , prepositioned vowels have longer phona lion time than postpositioned vowels and the intrin, iii phonation time is whore longer in the low vowels than in the high ones. The africative consonants show the mixed characteristics of the plosive and frlc ative consonants. The remarkable acoustic cues are the low frequency noise-like waves just before the 1st formants in the plosive consonants, the high frequency noise-like waves in the fricative consonants, and phonation time is not affected by the kinds of prepositioned or postpositioned vowels.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.489-492
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• 2000

Film Bulk Acoustic Wave Resonator(FBAR) used in microwave region was analyzed with Finite Difference Time-Domain Methods(FDTD) in this paper. FBAR have been analyzed with one dimensional Mason model analysis or Finite Element methods(FEM), but the first couldn't analyze effect of area variation and spurious characteristics, the second had difficulty in element separation because of thin electrode. So in this paper FBAR was analyzed by Finite Difference Time-Domain Methods and it's results were transformed to frequency domain using Discrete Fourier Transform.