• Journal of the Korea Convergence Society
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• v.10 no.9
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• pp.193-198
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• 2019

This study analyzed the changes of vowel formant, voice intensity, and fundamental frequency of vowels for 11 months using acoustochemical spectrogram analysis of women diagnosed with amyotrophic lateral sclerosis (ALS). The test word was a vowel /a, i, u/ and a diphthong /h + ja + da/, /h + wi + da/, and /h +ɰi+ da/. Speech data were collected through the word reading task presented on the monitor using 'Alvin' program, and the recording environment was set to 5,500 Hz for the nyquist frequency and 11,000 Hz for the sampling rate. The records were analyzed by using spectrograms to vowel formants, voice intensity, and fundamental frequency. As a result of analysis, the fundamental frequency and intensity of the ALS process were decreased and the formant slope of the diphthong was decreased rather than the formant change in the vowel. This result suggests that the vowel distortion of ALS due to disease progression is due to the decrease of tongue and jaw co morbidity.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.252-252
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• 2022

최근 기존의 전통적인 부유사채집기를 활용한 유사량 측정방법의 대안으로 지속적인 유량측정을 목적으로 활용되고 있는 횡방향 초음파도플러유속계의 초음파산란도를 활용하여 부유사농도를 측정에 대한 연구가 수행되고 있다. 하지만, 하천에서 횡방향 초음파도플러유속계를 활용한 유사량 측정 연구는 현장에서 측정된 자료를 기반으로 분석이 수행되기 때문에 통제된 유사 조건에서의 유사의 농도 및 입도분포에 대한 사전 정보를 바탕으로 정밀한 분석의 어려움이 있다. 이에 본 연구에서는 안동하천실험센터 순환수로에서 균일한 입도를 가지고 있는 황토를 활용하여 주입량에 따른 초음파산란도의 변화와 동시에 측정된 LISST(laser in-situ scattering and transmissometry)의 부유사 농도와 입도 자료를 활용하여 유사공급에 따른 3Mhz의 단일 주파수를 사용하는 횡방향 초음파도플러유속계의 초음파산란도를 활용한 부유사농도 및 평균입경의 측정에 대한 연구를 수행하였다. 측정결과, 유사공급에 따라서 초음파산란도를 활용하여 부유사농도가 증가하는 경향을 나타내고 있었으며, 횡방향 초음파도플러유속계로부터 측정된 셀별 초음파산란도를 활용하여 부유사농도의 공간적인 분포의 분석이 가능함을 확인할 수 있었다. 그리고 유사감쇄계수를 활용하여 LISST로부터 측정된 평균입경과의 관계식을 개발하여 유사공급에 따른 평균입경의 변화를 측정할 수 있을 것으로 나타났다. 추후, 통제된 조건에서의 다양한 입도분포에 따른 실험을 통해 횡방향 초음파도플러유속계의 초음파산란도를 활용한 부유사농도 측정 정확도를 개선과 유사감쇄계수를 통해 평균입경을 측정하는데 활용이 될 것으로 판단된다.

• The Journal of the Acoustical Society of Korea
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• v.13 no.6
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• pp.75-82
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• 1994

The ray paths and travel times of sound wave in the ocean depend on the physical properties of the propagating media. Ocean Acoustic Tomography(OAT), which is inversely estimate the travel time variations between fixed sources and receivers the physical properties of the corresponding media can he understood. To apply ocean survey technology by using the OAT, the tomographic procedure requires forward problem that variation of the travel times be identified with the variability of the medium. Also, received signals must be satisfied the necessary conditions of ray path stability, identification and resolution in order for OAT to work. The canonical ocean has been determined based on the historical data and its travel time and ray path are used as reference values. The sound speed of canonical ocean in the East Sea is about 1523 m/s at the surface and 1458 m/s at the sound channel axis(400m). Sound speeds in the East Sea are perturbed by warm eddy whose horizontal extension is more than 100 km with deeper than 200 m in depth scale. In this study, an acoustic source and receiver are placed at the depth above the sound channel axis, 350 m, and are separated by 200 km range. Ray paths are identified by the ray theory methed in a range dependent medium whose sound speeds are functions of a range and depth. The eigenray information obtained from interpolation between the rays bracketing the receiver are used to simulate the received signal by convolution of source signal with the eigenray informations. The source signal is taken as a 400 Hz rectangular pulse signal, bandwidth is 16 Hz and pulse length is 64 ms. According to the analysis of the received signal and identified ray path by using numerical model of underwater sound propagation, simulated signals satisfy the necessary conditions of OAT, applied in the East Sea.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.1
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• pp.33-41
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• 1998

The response characteristics of the PZT transducers during glass capillary breakage were studied at the epicenter of the glass plate. The PZT transducers had been made by using EC-65 PZT ceramics(supplied by Edo co.) with a constant area and a various thickness. The theoretical displacement and velocity at the epicenter of glass plate with an air boundary condition were calculated by assuming the point load of 1N force strength and a rise time of 280 ns with a ramped functional dependence, and the 1st pulses of the PZT transducer may be considered as the vertical velocity incident on the electrode of the PZT ceramic. The responses of the PZT transducer may be depended on the thickness mode of the PZT ceramic below 0.33 in the ratio of the thickness to the diameter of PZT ceramic, but the reponse of the PZT transducer may be depended on the other modes of PZT transducer in the addition of the thickness mode of the PZT ceramic above 0.33. The full time of half maximum at the 1st pulse was nearly 280 ns without a variation of applied breakage load and the resonant frequency of the PZT transducer, and then may be considered as the rise time of a AE source. The maximum amplitude of the 1st pulse depended on the incident vertical velocity and capacitance of the PZT transducer. Therefore, the full time of half maximum and maximum amplitude of the 1st pulse may be considered as the rise time and strength of acoustic emission source respectively.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.5
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• pp.370-376
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• 2016

Corrosion on the surface of a structure can generate cracks or cause walls to thin. This can lead to fracturing, which can eventually lead to fatalities and property loss. In an effort to prevent this, laser imaging technology has been used over the last ten years to detect thin-plate structure, or relatively thin piping. The most common laser imaging was used to develop a new technology for inspecting and imaging a desired area in order to scan various structures for thin-plate structure and thin piping. However, this method builds images by measuring waves reflected from defects, and subsequently has a considerable time delay of a few milliseconds at each scanning point. In addition, the complexity of the system is high, due to additional required components, such as laser-focusing parts. This paper proposes a laser imaging method with an increased scanning speed, based on excitation and the measurement of standing waves in structures. The wavenumber of standing waves changes at sections with a geometrical discontinuity, such as thickness. Therefore, it is possible to detect defects in a structure by generating standing waves with a single frequency and scanning the waves at each point by with the laser scanning system. The proposed technique is demonstrated on a wall-thinned plate with a linear thickness variation.

• Journal of Oral Medicine and Pain
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• v.30 no.4
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• pp.427-432
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• 2005

This study have been compared and analyzed voice parameter under the condition of normal voice and auditory condition(noise and music) for 29 patients of orofacial pain and 31 normal people to investigate voice feature and vocal variation for auditory condition of orofacial pain patient. 1. Compared to normal voice, orofacial pain patient showed lower and unstable voice feature which has low F0 rate and high jitter and shimmer rate. 2. Voice of orofacial pain patient showed more relaxed and stable voice feature with low F0 and shimmer rate in the music condition than noise condition. 3. Normal people's voice has no significant difference between music and noise condition even though it has high F0 rate under the noise condition. As a result, orofacial pain patient showed difference of feature and different response for external auditory condition compared to normal voice. Providing of positive emotional environment such as music could be considered for better outcome of oral facial pain patient's functional disability.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.87-94
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• 2017

Because the cavitation flow driven by an underwater propeller corrodes the materials around it and generates a high level of noise, it has become an important topic in engineering research. In this study, computational fluid dynamics techniques are applied to simulate cavitation flow, and the noise in the flow is predicted by applying the acoustic analogy to the predicted flow. The predicted results are compared with measurement results and other predictions in terms of surface pressure distribution and the temporal variation in liquid volume fraction. The predicted results are found to be in good agreement with the measured results. The source of the noise attributed to the time rate of change in the liquid volume fraction around the hydrofoil is modeled as a monopole source, and the source of the noise due to unsteady pressure perturbations on the hydrofoil surface is modeled as a dipole source. Then the predicted noise results are analyzed in terms of directivity and SPL spectrum. The noise caused by unsteady pressure perturbations was dominant in the entire frequency range considered in the study.

• Journal of the Korean Society of Marine Environment & Safety
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• v.12 no.4 s.27
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• pp.301-306
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• 2006

In order to estimate the characteristics of water movements around artificial upwelling structure, current measurements were carried out along lines E-W and S-N on May 4th(neap tide} and May 30th(spring tide), 2006. In the study area, southeastward flow was dominant during the field observations, and the pattern of water movement in the upper layer above 30m depth was different from that in the lower layer below 30m depth Vertical flow(w-component} around the artificial structure area and western area was shown to be upward flow, but downward flow occurred in the southern, northern and eastern parts at the neap tide. At the spring tide, the ebb current along E-W line showed upwelling flow in the eastern part and western area and showed upwelling flow near the artificial structure area and downwelling flow far away that one. At the spring tide, upward flow was dominant along S-N line during the flood current Volume transport by upward flow was higher than that by downward flow. Volume transport by upward flow during ebb of neap tide was greater than during flood current of neap tide, but was reverse at the spring tide.

• Geophysics and Geophysical Exploration
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• v.4 no.4
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• pp.115-123
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• 2001

The bright spot is an indicator for natural gas on seismic stack sections, but it is also shown on layers where the acoustic impedance contrast is large. In order to distinguish sharply between gas and impedance contrast we need additional detailed data processing such as velocity analysis, AVO analysis and seismic complex analysis including measures of seismic amplitude, frequency, and phase. In this study, we performed detailed velocity analysis, complex analysis and DHI (Direct Hydrocarbon Indicator) analysis which is the result of amplitude variation according to the incident angles. The seismic complex analysis gives us the geological information which depends on geophysical properties at the interest layer. For the complex analysis, we computed several seismic attributes such as the instantaneous amplitude, the first and the second derivatives of the instantaneous amplitude, the instantaneous phase, the instantaneous frequency and weighted average instantaneous frequency. Then we applied these analysis techniques to a seismic data of Korea offshore which had been logged. From the result of this data analysis, it could be said that high possibility area for gas layer detection has amplitude anomalies in the instantaneous amplitude, the instantaneous frequency and the DHI section resulting from the AVO analysis. If there are not any other anomalies in detailed data processing, it will have low possibility for gas layer detection.

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.94-98
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• 2006

An optical microphone based on a dual-core fiber collimator and a membrane type micromirror serving as an optical head and a reflective diaphragm respectively was implemented. The micromirror diaphragm is suspended by a thin silicon bar linked with a frame, thus it is subject to a displacement induced by acoustic waves. The optical head incorporating two collimators integrated in a single housing gives light to and receives it from the diaphragm, rendering the optical microphone structure simple and compact. This dual-core collimator having a slowing varying beam profile facilitates the initial alignment of the optical head with the diaphragm, especially the distance between them. For the assembled microphone, the static characteristics were investigated tofind the operation point defined as the optimum distance between the head and the diaphragm, and a frequency response with a variation of about $\pm$5 dB for the range of up to 3kHz was achieved.