• Geophysics and Geophysical Exploration
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• v.2 no.1
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• pp.33-42
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• 1999

AVO and complex trace analyses mainly used to characterize natural gas reservoir were tested in this paper for a possible application to detection of major geological discontinuities such as fracture zones. The test data used in this study were calculated by utilizing a viscoelastic numerical program which was based on the generalized Maxwell body for a horizontal fracture model. In AVO analysis of a horizontal fracture zone, p-wave reflection appears to be variant depending upon the acoustic-impedence contrast and the offset distance. The fracture zone is also effectively clarified both in gradient stack and range-limited stack in which fracture zone reflection is attenuated with the increasing offset distance. In complex attribute plots (instantaneous amplitude, frequency, and phase), the top and bottom of the fracture Tone are characterized by a zone of strong amplitudes and an event of the same phase. Low frequency characteristics appear at the fracture zone and the underneath. Amplitude attenuation and waveform dispersion are dependent on Q-contrast between the fracture zone and the surrounding media. They were properly compensated by optimum inverse Q-filtering.

• The Journal of the Acoustical Society of Korea
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• v.24 no.2
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• pp.78-86
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• 2005

This study considers the magnitude of the harmonic components radiated from the ultrasonic contrast agents (UCA) activated by a typical diagnostic ultrasound. The nonlinear dynamic response of UCA to a 2 MHz diagnostic ultrasound pulse was predicted using Gilmore Model. The elastic property of the shell membrane of the UCA was ignored in the numerical model. Simulation was carried out for the UCA varying from 1 - 9 $\mu$m in its initial radius and the driving diagnostic ultrasound whose mechanical index (MI) ranges from 0.125 to 8. The powers of the sub. ultra and second harmonics of the acoustic signal from the UCA activated were compared with that of the fundamental component. The results show that. if the UCA is bigger than its resonant size (2 $\mu$m in radius for the present case) the sub harmonic power was much bigger than the fundamental. In particular, the 2nd harmonic component currently used as an imaging parameter for the harmonic imaging, was predicted to be lower in power than both the sub and the ultra harmonic component. This study indicates that, for obtaining harmonic imaging with UCA, the sub or ultra harmonics could be taken as imaging parameters better than the 2nd harmonic component.

• Journal of Digital Contents Society
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• v.14 no.3
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• pp.323-331
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• 2013

This study aims at investigating and comparing the diphthongs, words, and sentences between two Korean highschool students groups using the Praat program. To do this English words and sentences were uttered and recorded by twenty Korean subjects; each group has ten subjects. All the subjects are female and their grades range from freshman to sophomore. Acoustic features were measured from a sound spectrogram with the help of the Praat software program and analyzed through statistical analysis. Results showed that the lengths of diphthongs and words were different between two groups, but the difference was not significant. However, in the lengths of sentence utterance, the group of 5 to 6 grade students in the current grading system pronounced longer than that of 1 to 2 grade students. Especially in the pronunciation of the first two sentences with more than five words, the difference was significant. From the data of the overall sum of words between the two subject groups, we were able to find out that the differences of the lengths of the words with the diphthongs were not significant, but those of the sentences with more than five words were significant. In the pronunciation of the words between coat and code, the length of the diphthong in coat was smaller than that of in code.

• Journal of Internet Computing and Services
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• v.18 no.1
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• pp.57-64
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• 2017

Recent automobile manufacturing technology has improved not only the function and performance of cars, but also the audio systems in cars so as to increase their marketability. Automobile manufacturers always have the option of simply installing an expensive acoustic system to help customers enjoy a high-level sound quality car audio system. However, this also tends to increase the MSRP (Manufacturer's Suggested Retail Price) of the car. Therefore, it is desirable, where possible, to enhance the sound quality of plainer, less expensive audio devices to help customers feel as if they have a high-quality and expensive audio device in their car. In order to make this happen, the manufacturer must develop an optimal interior environment and audio system at a relatively lower cost. To this end, features of the car audio system can be enhanced by analyzing audio frequency response and using performance metrics to figure out the characteristics of the human auditory system. This study analyzed the sound field of Korean Recreation Vehicles (RVs) using the Internet of Things (IoT) sensor for the measurement of car audio system. As a result, high energy of sensitive bandwidth, one of the human auditory characteristics often makes annoying sound. This study also found that increasing the frequency response flatness is required by taking human auditory field into account when designing the car audio system for the future.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.17 no.2
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• pp.107-110
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• 2006

Background and Objeetives : There are few studies reported that specifically examined the voice onset time(VOT) in patients with bilateral vocal nodules. The purpose of this study was to study the characteristics of voice onset in patients with bilateral vocal nodules. Materials and Methods : 52 female patients with bilateral vocal nodules were examined, aged from 20 to 54 years, and were compared with 25 normal female control group. All subjects produced five repetitions of the voiceless stops $/p^h,\;t^h\;k^h/$ in vowel context /ai_a/. VOT was measured by the time between the release of the stops and the onset of voicing. Results : VOTs of the voiceless stops $/p^h/\;and\;/t^h/$ in patients with bilateral vocal nodules were significantly shorter than those of normal subjects. VOT of the $/k^h/$ in them was shorter than those of normals, but the difference was not significant. This results showed that VOTs of the voiceless stops in patients with bilateral vocal nodules were shorter than those of normal subjects. Conclusion : The rapid onset of voicing in patients with bilateral vocal nodules might be associated with increased laryngeal muscle tension by hard glottal attacks. We suggest that VOT can be a clinically useful acoustic parameter for evaluating voice in patients with bilateral vocal nodules.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.2
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• pp.129-138
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• 2005

Sediment texture, physical (porosity, water content, bulk density, grain density, and shear strength), and geoacoustic properties (compressional wave velocity and attenuation) were measured on eighteen core samples collected from the shelf off eastern Geoje Island, the South Sea of Korea. Based on these properties, the study area is divided into three different sub-areas: (1) Area I affected directly by the Nakdong River discharge; (2) Area II covered by the southern branch of the Nakdong River discharge; and (3) Area III dominated by relict sediment. Mean grain size, velocity, and bulk density decrease from Area $I(7.4\Phi,\;1528m/s,\;1.6g/cm^3,\;respectively)$ to Area $II(8.1\Phi,\;1485m/s,\;and\;1.5g/cm^3)$, and then increase rather rapidly in Area $III(1.4\Phi,\;1664m/s,\;and\;2.2g/cm^3)$. Porosity, on the other hand, exhibits an opposite trend, increasing from Area $I(64.5\%)$ to Area$II(73.9\%)$ and then decreasing significantly in Area $III(32.9\%)$ From the results measured and calculated, we suggest a specified geoacoustic model in the study area.

• Journal of Korea Water Resources Association
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• v.40 no.12
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• pp.957-968
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• 2007

It is essential to obtain accurate and highly reliable streamflow data for quantitative management for water resources. Thereafter such real-time streamflow gauging methods as ultrasonic flowmeter and index-velocity are introduced recently. Since these methods calculate flowrate through entire cross-section by measuring partial velocities of it, rational and theoretical basis are necessary for accurate estimation of discharge. The purpose of the present study lies in analysis on the applicability of Chiu#s(1987, 1988) two dimensional velocity distribution equations by applying them to natural rivers and by comparing simulated velocity distributions with observed ones obtained with ADCP. Maximum and mean velocities are calculated from observed data to estimate entropy parameter M. Such isovel shape parameters as h and $\beta_i$ are estimated by object function based on least squares criterion. In case optimized parameters are applied, Chiu#s velocity distributions fairly well simulate observed ones. By using 14 simulated data sets which have relatively high correlation coefficients, properties of parameters are analyzed and h, $\beta_i$ are estimated for velocity-unknown river sections. When estimated parameters are adopted for verification, simulated velocity distributions well reproduce real ones. Finally, calculated discharges display rough agreement with measured data. The results of the present study mean that if parameters related are properly estimated, Chiu#s velocity distribution is likely to reproduce the real one of natural rivers.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.20 no.1
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• pp.63-67
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• 2009

Background and Objectives: In patients with asthma, increased obstruction and resistance of airway result in impairment in the generation of voice. Allergy and nasal polyposis, which are frequently observed in patients with asthma, are other factors that affect the vocal performance. Bronchodilators and steroids are commonly used in the treatment of asthma, and these agents also have been reported to be associated with voice changes. The aim of this study is to evaluate the voice quality in patients with mild to-moderate asthma by subjective and objective methods. Materials and Methods: A total of 36 patients with asthma established in the Department of Respiratory Medicine were included in this study. 23 were women and 13 were men, with a mean age of 51.7 years. The average duration of asthma was 77.0 months. All patients had mild-to moderate asthma. Acoustic and aerodynamic analyses were performed and the movements of the vocal cords were examined by videolaryngostroboscopy (VLS). Voice Handicap Index (VHI) and GRABS scales were used for subjective evaluations. Results: 50% of patients suffered from dysphonia and FO was 119.3${\pm}$23.7 Hz in male and 198.2${\pm}$18.4 Hz in female patients. There were no significant differences in average shimmer and NHR between females (4.90${\pm}$2.95% ; 0.1O${\pm}$0.04 dB) and males (4.64${\pm}$2.45% ; 0.20${\pm}$0.15 dB). However, the value of jitter was greater for females (2.60${\pm}$1.92%) than for males (1.21${\pm}$0.84%). The VHI score was above the normal limit in 35%, and VLS findings were shown diverse abnormality in 89% asthmatics from mucosal change to hyperfunction of supragottis and contact granuloma. But duration of illness and steroid dose did not correlate with these findings. Conclusion: Subjective and objective abnormality was shown in more than 50% of asthmatic patients. We suggest that persons who suffer from asthma should be examined for possible voice disorders by laryngologist. Additionally, appropriate medical care and voice therapy should be provided for those who have voice disorders associated with asthma.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.28 no.2
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• pp.118-122
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• 2017

Background and Objectives : In unilateral vocal fold paralysis (VFP), medialization thyroplasty (MT), arytenoid adduction (AA) and injection layrngoplasty (IL) are the most common procedures to correct phonatory problems. There is no consensus that which procedure is superior to the other for correcting the glottal insufficiency. The purpose of this study was to compare the phonatory parameters between MT, AA and AA with IL (AA+IL) in patients with unilateral VFP. Materials and Methods : This retrospective study enrolled patients from 2005 to 2016. Total 72 patients (49 male, 23 female, mean age 54.5 years) were classified into three groups ; MT (n=28), AA (n=12), and AA+IL (n=32). GRBAS scales, maximum phonation time (MPT), jitter, shimmer, noise to harmonic ratio (NHR), and voice handicap index (VHI)-10 and VHI-30 were preoperatively and postoperatively collected and compared between the three groups. Results : Age, gender and cause of VFP were not significantly different between the three groups. In MT and AA groups, MPT, VHI, G (overall grade) and B (breathiness) were significantly improved. In AA+IL group, jitter, shimmer, NHR, MPT, VHI, G and B were significantly improved. In analysis of differences (pre-postoperative values), ${\Delta}$ jitter (p<0.001), ${\Delta}$ shimmer (p=0.031), and ${\Delta}$ NHR (p=0.002) were significantly different and AA+IL group showed the greatest improvement. Conclusion : Analysis of voice parameters showed that all the three procedures for patients with unilateral VFP are effective in the improvement of voice ; especially in MPT, VHI-10, G and B scales. Compared to the others, AA+IL provided the better acoustic values including jitter, shimmer and NHR.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.2
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• pp.85-94
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• 2001

The vertical distribution and activity patterns of fishes during the evening and morning transitions were investigated acoustically and by pelagic trawling on October 2-10, 1997 in the Korean Eastern Sea. The acoustic data were collected from four stations with a scientific echo sounder operating at a frequency of 38 kHz, and the echogram was used to analyze the diel vertical migration of fish. Biological sampling was accomplished by pelagic trawling to identify fish species recorded on the echograms, and the species and length compositions were investigated. Vertical profiles of water temperature, salinity at the trawl station were taken with a CTD system and were related to the diel movement and the depth distribution of fish. During the day, one group of fish mainly distributed above the depth layer of 50 m, the other group was at deeper water, approximately 250 m, but began to migrate toward the surface before sunset with a time difference. During the night, they were dispersed between the surface and the depth of 125 m. Just prior to sunrise, the scattering layer was divided with 2 groups and began to migrate downwards, respectively. Several trials of pelagic trawling for scattering layers suggest that the most dominant scatterer in the survey area of this study was Japanese flying squid, Todarodes pacificus..