• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.28-35
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• 2002

In cavity flow, the rectangular step generates so strong sound that many researchers have investigated method to suppress the nois during interaction between vortical flow and rectangular forward step. In this study the flow noise from the vortex motion in two-dimentional low Mach number flow past a forward step with various chamfering angle is calculated numerically. Inviscid incompressible discrete vortex model and matched asymptotic expansion(MAE) theory are applied to obtain the inner flow field and the outer noise field. Both source acoustic pressure and sound intensity are obtained with various chamfering height, chamfering angle and initial vortex position. The pressure amplitude is most suppressed when the chamfering angle is between $15^{\circ}C$ and $30^{\circC}$ at the chamfering length of 30% of the step height.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.137-140
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• 2008

During CHAOS (2003, 2006) and SSGH projects (2007), acoustic investigation including hydroacoustic (HA), side-scan sonar (SSS) and highresolution sparker seismic (HSS) surveys was carried out on the northeastern Sakhalin slope ($53^{\circ}56'\;N$, $143^{\circ}52'\;E$ to $54^{\circ}40'\;N$, $144^{\circ}32'\;E$). More than 130 methane seeps with high backscatter intensity are identified on SSS mosaic, which are well accompanied with gas flares in the water column on HA profiles and subbottom gas chimneys on HSS profiles. It is likely that that some seeps align along a NW strike parallel to the Lavrentiev Fault.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9B
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• pp.1551-1562
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• 2000

In the using of FBG developed in home land, we designed and manufactured three types of FBG sound transducers the first in Korea. On FBG transducers manufactured we made an demonstrated on respective frequency response peculiarties in the water and analyzed the special characters. As the experimental result on frequency response peculiarities, we made t possible underwater acoustic detection on C type to maximum 18kHz, And for the purpose of realization on multi-point signal detection on wide scope in the water, in the using of WDM(Wavelength Division Multiplexing) method and passive band-pass filter system, established arrays system and succeeded in multi-point underwater acoustic signal detection to the frequency 1.3KHz out of the two B type FBG transducers. Additionally, it would be possible directivity detection for the objects of its source as the intensity of detection signal varies with the sound source's direction and angle. From now on we prepared a new moment on the practical used study on FBG hydrophone.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.1
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• pp.30-40
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• 2002

This paper studies the electronic ballast development for 250w MH lamps. We have improved the input power factor using a PFC IC. To provide the rating voltage required In the lamps, we have used the buck type dc-dc converter By this method, the stress of switching devices in inverter can be reduced. The inverter is the Full-Bridge type. To eliminate the acoustic resonance phenomena of MH lamps, we have added the high frequency sinewave voltage to the low frequency square-wave voltage to the lamp. We hove developed the igniter circuit using the L, C devices. We could control dimming of the lamp by varying the output voltage of the buck converter. The time of illuminating lamps and luminous intensity could be adjusted by season and time band. The buck converter output voltage can be controlled and the no load and over current situation were Protected by the development of the microprocessor Program.

• 한국해양학회지
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• v.24 no.4
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• pp.172-183
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• 1989

Acoustical estimation of vertical distributions of zooplankton was carried out by using the backscattered signals of ADCP which was deployed in the Korea Strait in September, 1978. the backscattered signals of ADCP represents the total backward sound intensity caused by the scatters existing within the insonified water column of 8m deep. Based on these backscattered intensities, the estimated number of individual zooplankton (namely, Copepods) varies with depth such that in the surface layer above the thermocline, the numbers are exceedingly larger than the lower layer. It is also shown that a relatively larger number of individuals exists in the bottom cold water layer in the centeral part of the Strait. The horizontal distribution of the zooplankton in the surface layer across the west channel of the Strait shows that the number is higher in the coastal zone of the Korea and it decreases toward the central and then remains constant up to the vicinity of the Tsushima Island where it increases again. This type of distributions is well fitted to the one obtained at several stations by the conventional method at least in qualitative way. Therefore, it is quite plausible to use the ADCP data for monitoring the spatial and temporal distributions of zooplankton.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.24 no.1
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• pp.33-40
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• 2013

Background and Objectives:This study is to objectively compare and analyze the acoustic changes in the patients with total thyroidectomy before and after RI therapy. Subjects and Methods:For this study, a total of 50 patients with total thyroidectomy were participated as subjects. Voice samples were obtained at the time of post-operation (Post-OP), before high-dose radioactive iodine therapy (Pre-RIT), and after high-dose radioactive iodine therapy (Post-RIT). Acoustic analysis, the maximum phonation time and K-VHI (Korea-Voice handicap index) were used for subjective evaluation. Results:According to the comparison analysis of the three periods, mFo (Hz) was significantly reduced in all of the vowels /a/ and /i/ as the hormone was discontinued. This can be related to the reduction in vocal range. As thyroid hormone was discontinued, Shim (%) and APQ (%) values, which are the parameters related to the degree of aggressiveness, showed a significant increase in the middle vowel /a/. As thyroid hormone was discontinued, emotional index was significantly decreased in VHI (voice handicap index). Conclusion:These results can be assumed that thyroid hormone suspension is related to the increased changes in the vocal intensity, the increase in noise and the reduction in vocal range. Emotionally, these data can be assumed that the responsive factors of one's own voice disorders were significantly decreased in the patients with vocal handicap.

• Journal of Biomedical Engineering Research
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• v.39 no.6
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• pp.250-255
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• 2018

Accurate blood typing is the crucial factor for safe and successful blood transfusion and plays a very important role in organ transplantation and genetic information of forensic medicine. Microfluidic devices have been developed to overcome the limitations of the conventional blood typing methods. In this study, we demonstrate a Lamb wave-based device for simple blood typing in a sample droplet and we propose new indices for quantitative and accurate blood typing. Using Lamb wave-induced acoustic streaming in the droplet, the blood sample and the reagent can be mixed rapidly and red blood cells start to form clumps, which is agglutination. Based on the recorded image and video, the intensity of transmitted light through the sample droplet is evaluated to determine the blood type. Effect of the concentration of suspended red blood cells was evaluated and we found that 10% concentration of suspended red blood cells was suitable to observe the difference between aggregated and non-aggregated samples. Finally, sample with blood type A could be determined using anti-A reagent in our Lamb wave-based device. Our device enables simple and accurate blood typing, which can be applied to resource-limited environments.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.12
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• pp.93-102
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• 1998

In noisy environments, human speech productions are influenced by noises(Lombard effect), and speech signals are contaminated. These distortions dramatically reduce the performance of speech recognition systems. This paper proposes a method of the Lombard effect compensation and noise suppression in order to improve speech recognition performance in noise environments. To estimate the intensity of the Lombard effect which is a nonlinear distortion depending on the ambient noise levels, speakers, and phonetic units, we formulate the measure of the Lombard effect level based on the acoustic speech signal, and the measure is used to compensate the Lombard effect. The distortions of speech under noisy environments are cancelled out as follows. First, spectral subtraction and band-pass filtering are used to cancel out noise. Second, energy nomalization is proposed to cancel out the variation of vocal intensity by the Lombard effect. Finally, the Lombard effect level controls the transform which converts Lombard speech cepstrum to clean speech cepstrum. The proposed method was validated on 50 korean word recognition. Average recognition rates were 82.6%, 95.7%, 97.6% with the proposed method, while 46.3%, 75.5%, 87.4% without any compensation at SNR 0, 10, 20 dB, respectively.

• Science of Emotion and Sensibility
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• v.16 no.1
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• pp.117-124
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• 2013

This study examined that how precisely MFCC, LPC, energy, and pitch related parameters of the speech data, which have been used mainly for voice recognition system could predict the vocal emotion categories as well as dimensions of vocal emotion. 110 college students participated in this experiment. For more realistic emotional response, we used well defined emotion-inducing stimuli. This study analyzed the relationship between the parameters of MFCC, LPC, energy, and pitch of the speech data and four emotional dimensions (valence, arousal, intensity, and potency). Because dimensional approach is more useful for realistic emotion classification. It results in the best vocal cue parameters for predicting each of dimensions by stepwise multiple regression analysis. Emotion categorizing accuracy analyzed by LDA is 62.7%, and four dimension regression models are statistically significant, p<.001. Consequently, this result showed the possibility that the parameters could also be applied to spontaneous vocal emotion recognition.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2208-2213
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• 2007

In this study we have developed a hyperspectrum imaging system for highly sensitive and effective imaging analysis. An optical setup was designed using acoustic optical tunable filter (AOTF) for high sensitive hyperspectrum imaging. Light emitted by mercury lamp gets split in to diffracted and undiffracted beams while passing though AOTF. GFP transfected HEK-293 cell line was used as a model for in vitro imaging analysis. Cells were first, analyzed by fluorescence microscope followed by flow cytometric analysis. Flow cytometric analysis showed 66.31% transfection yield in GFP transfected HEK-293 cells. Various images of GFP transfected HEK-293 cell were grabbed by collecting the diffracted light using a CCD over a dynamic range of frequency of 129-171 MHz with an interval of 3 MHz. Subsequently, for in vivo image analysis of GFP transfected cells in mouse, a whole-body-imaging system was constructed. The blue light of 488 nm wavelength was obtained from a Xenon arc lamp using an appropriate filter and transmitted through an optical cable to a ring illuminator. To check the efficacy of the newly developed whole-body-imaging system, a comparative imaging analysis was performed on a normal mouse in presence and absence of Xenon arc irradiation. The developed hyperspectrum imaging analysis with AOTF showed the highest intensity of green fluorescent protein at 153 MHz of frequency and 494 nm of wavelength. However, the fluorescence intensity remained same as that of the background below 138 MHz (475 nm) and above 162 MHz (532 nm). The mouse images captured using the constructed whole-body-imaging system appeared monochromatic in absence of Xenon arc irradiation and blue when irradiated with Xenon arc lamp. Nevertheless, in either case mouse images appeared clearly.