• Composites Research
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• v.20 no.3
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• pp.55-62
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• 2007

Interfacial evaluation and durability of Jute and Hemp fibers/polypropylene (PP) composites were investigated. Moisture content of various treated conditions were measured by thermogravimetic analyzer (TGA). After boiling water test, mechanical properties and IFSS between Jute, Hemp fibers and PP matrix decreased. On the other hand, work of adhesion increased due to swelled fibril by water. Surface energies of Jute and Hemp fibers before and after boiling water test were obtained using dynamic contact angle measurement. IFSS was not always consistent with thermodynamic work of adhesion. In boiling water case, since Jute and Hemp fibers could be swelled by water, surface area and moisture infiltration space increased. Environmental effect on microfailure modes of Jute or Hemp fibers and Jute or Hemp fibers/PP composites were obtained by observing via optical microscope and by monitoring acoustic emission (AE) events and their AE parameters. After boiling water test, unlike Hemp fiber, microfailure process of Jute fiber could occur due to low tensile strength by swelled fibril. In addition, AE events occurred more and AE amplitude and energy became lower than those of before boiling water test.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.22 no.1
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• pp.40-46
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• 2011

Background and Objectives : Vocal fold bowing is an organic voice disorder that is associated with an abnormal structure of the vocal folds whereas vocal fold polyp is a functional voice disorder caused by an abnormal use of the vocal folds. Both types of vocal folds share a common property in that they make one's voice breathy or strained. The purpose of this study is to compare voice from two types of vocal folds and to offer information of clinical importance. Materials and Method: Vocal fold bowing and vocal fold polyp groups consisted of 7 male subjects, respectively. All subjects recorded /a/ in the state of measuring MPT (maximum phonation time), repeating 3 times, by a voice recorder (48 kHz sampling rate; 24 bit quantization). They answered the questions of K-VHI. Time domain parameters (such as perturbation parameters including HNR, Jitter, etc.) were calculated for the whole duration of /a/ and those of the frequency domain were measured in initial 40 ms and stable 40 ms of /a/, respectively. Mann-Whitney V-test was used for the time domain parameters and K-VHI survey, and Wilcoxon signed rank test was applied to the frequency domain parameters (H1, H2, H1-H2). Results: For K-VHI survey and the time domain analysis, there was no significant difference between bowing and polyp group. For frequency domain analysis, H1 and H2 showed a significantly different result between two groups. Vocal fold bowing group has longer duration and lower intensity than that of vocal fold polyp group in the 'aspirated interval', which could be observable prior to ordinary vowel oscillation. Conclusion: Both groups seem to show breathy voice. This could be referred on the basis of the value of H1-H2. The K-VHI survey says that subjects with vocal fold bowing feel more uncomfortable than subjects with vocal fold polyp.

• The Journal of the Acoustical Society of Korea
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• v.40 no.2
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• pp.139-147
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• 2021

This paper introduces and implements a Sound Event Detection (SED) system based on weakly-supervised learning where only part of the data is labeled, and analyzes the effect of parameters. The SED system estimates the classes and onset/offset times of events in the acoustic signal. In order to train the model, all information on the event class and onset/offset times must be provided. Unfortunately, the onset/offset times are hard to be labeled exactly. Therefore, in the weakly-supervised task, the SED model is trained by "strongly labeled data" including the event class and activations, "weakly labeled data" including the event class, and "unlabeled data" without any label. Recently, the SED systems using the mean-teacher model are widely used for the task with several parameters. These parameters should be chosen carefully because they may affect the performance. In this paper, performance analysis was performed on parameters, such as the feature, moving average parameter, weight of the consistency cost function, ramp-up length, and maximum learning rate, using the data of DCASE 2020 Task 4. Effects and the optimal values of the parameters were discussed.

• The Journal of the Acoustical Society of Korea
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• v.21 no.2
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• pp.199-210
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• 2002

In this paper, we carried out the study on speech recognition using the KM-Net topology design algorithm based on decision tree state-clustering to improve the performance of acoustic models in speech recognition. The Korean has many allophonic and grammatical rules compared to other languages, so we investigate the allophonic variations, which defined the Korean phonetics, and construct the phoneme question set for phonetic decision tree. The basic idea of the HM-Net topology design algorithm is that it has the basic structure of SSS (Successive State Splitting) algorithm and split again the states of the context-dependent acoustic models pre-constructed. That is, it have generated. the phonetic decision tree using the phoneme question sets each the state of models, and have iteratively trained the state sequence of the context-dependent acoustic models using the PDT-SSS (Phonetic Decision Tree-based SSS) algorithm. To verify the effectiveness of the above algorithm we carried out the speech recognition experiments for 452 words of center for Korean language Engineering (KLE452) and 200 sentences of air flight reservation task (YNU200). Experimental results show that the recognition accuracy has progressively improved according to the number of states variations after perform the splitting of states in the phoneme, word and continuous speech recognition experiments respectively. Through the experiments, we have got the average 71.5%, 99.2% of the phoneme, word recognition accuracy when the state number is 2,000, respectively and the average 91.6% of the continuous speech recognition accuracy when the state number is 800. Also we haute carried out the word recognition experiments using the HTK (HMM Too1kit) which is performed the state tying, compared to share the parameters of the HM-Net topology design algorithm. In word recognition experiments, the HM-Net topology design algorithm has an average of 4.0% higher recognition accuracy than the context-dependent acoustic models generated by the HTK implying the effectiveness of it.

• Journal of Biosystems Engineering
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• v.33 no.1
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• pp.30-37
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• 2008

Dynamic excitation and response analysis is an acceptable method to determine some of physical properties of agricultural product for quality evaluation. There is a difference in the internal viscoelasticity between sound and defective fruits due to the difference of geometric structures, thereby showing different vibration characteristics. This study was carried out to develop a portable piezoelectric film-based glove sensor system that can separate internally damaged watermelons from sound ones using an acoustic impulse response technique. Two piezoelectric sensors based on polyvinylidene fluoride (PVDF) films to measure an impact force and vibration response were separately mounted on each glove. Various signal parameters including number of peaks, energy ratio, standard deviation of peak to peak distance, zero-crossing rate, and integral value of peaks were examined to develop a regression-estimated model. When using SMLR (Stepwise Multiple Linear Regression) analysis in SAS, three parameters, i.e., zeros value, number of peaks, and standard deviation of peaks were selected as usable factors with a coefficient of determination ($r^2$) of 0.92 and a standard error of calibration (SEC) of 0.15. In the validation tests using twenty watermelon samples (sound 9, defective 11), the developed model provided good capability showing a classification accuracy of 95%.

• Korean Journal of Materials Research
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• v.5 no.1
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• pp.12-21
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• 1995

The study was performed to study the effects of strain rate on acoustics emission( AE) during bulging test in corrosive environmentsynthetic sea water. The strain rates used were in the range $4 \times 10^{-6}S^{-1}$ to $1 \times 10^{-4} \times S^{-1}$ and the parameters used to evaluate AE signal characteristics were AE hit and amplitude. It can be observed that the cumulative AE hit and average amplitude during fracture process increase highly at decreasing strain rates while the equivalent fracture strain and the crack length of circumferencial direction become decrease. The peak point of AE signal characteristic parameters approach to the first half of test. When the average amplitude per unit equivalent fracture strain was above 20dB, it was definitly observed stress corrosion cracking phenomena. Additional, we knew that the AE test had the possibility to evaluate SCC susceptibility with various strain rates.

• Science of Emotion and Sensibility
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• v.3 no.2
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• pp.17-28
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• 2000

Psychoacoustic characteristics of automobile horns play significant role in resulting subjective evaluation and psychphysiological reactions. However, comparison and differentiation of physiological responses to commercially available horns is a complicated task due to the small contrast in technical features of horns and the influence of such processes as habituation on physiological outcome with the increased number of auditory stimulation trials. In a study on 10 college students, there was performed comparative analysis of reactivity of physiological responses mediated by central and autonomic nervous systems in order to identify the role of habituation on decrement of psychophysiological responsivity and assess the ability to differentiate subjectively most and least preferred, as well as most and least appropriate horns according to physiological manifestations. The EEG and autonomic responses to 7 automobile horns were analyzed during 3 blocks of trials, with varying order of stimuli and changed acoustic parameters of horns in each block. Thus, responses were analyzed for totally 21 trials of auditory stimulation. It was shown that electrodermal and cardiovascular responses have different reactivity patterns to repeated stimulation: skin conductance measures habituated, cardiac reactivity showed no signs of habituation, and the vascular response demonstrated sensitization. The temporal EEG exhibited marked habituation of fast beta band power, while alpha-blocking effect did not habituate during the course of experiment. Differentiation of physiological responses of most and least preferred and appropriate horns was possible in our study, however, some cardiovascular reactivity measures differentiated during the entire course of the experiment, while EEG and electrodermal parameters showed significant differences only during first block of trials, and were later affected by the habituation.

• Speech Sciences
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• v.9 no.2
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• pp.179-192
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• 2002

Our present study was performed to investigate acoustically the Korean normal adults' voices, with enough large number of subjects to be reliable. 120 Korean normal adults (60 males and 60 females) of the age of 20 to 39 years produced sustained three vowels, /a/, /i/, and /u/ and read a part of 'Taking a Walk' paragraph, and by analyzing them acoustically with MDVP of CSL, we could get the fundamental frequency ($F_{0}$), jitter, shimmer and NHR of sustained vowels: speaking fundamental frequency ($SF_{0}$), highest speaking frequency (SFhi), lowest speaking frequency (SFlo) of continuous speech. As results, on the average, male voices showed 118.1$\sim$122.6 Hz in $F_{0}$, 0.467$\sim$0.659% in jitter, 1.538$\sim$2.674% in shimmer, 0.117$\sim$0.114 in NHR, 120.8 Hz in $SF_{0}$, 183.2 Hz in SFhi, 82.6 Hz in SFlo. And, female voices showed 211.6∼220.3 Hz in F0, 0.678∼0.935% in jitter, 1.478∼2.582% in shimmer, 0.098∼0.114 in NHR, 217.1 Hz in $SF_{0}$, 340.9 Hz in SFhi, 136.0 Hz in SFlo. Among the 7 parameters, every parameters except shimmer showed the significant difference between male and female voices. And, when we compared the three vowels, they showed significant differences one another in shimmer and NHR of both genders, but not in $F_{0}$ of males and jitter of females.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.8
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• pp.1086-1094
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• 2020

AThis paper measured real sea area for performance analysis according to distance from west sea and south sea of Korea. The performance of the underwater OFDM system was analyzed by comparing the performance of the West and South Seas by adjusting the number of data repetitive transmissions and the pilot symbol placement interval parameters based on the real-sea data measured from the distance and Data rate of the West and South Sea vessels. In conclusion, when comparing the performance of the South Sea at the Data rate and distance, the BER performance of the South Sea was similar at the 5 km South Sea and 1 km West Sea under the same conditions. Placement interval of pilot symbol at 10 km of South Sea and 3 km of West Sea is (𝚫f, 𝚫t) = (6, 3) and the number of times the PRB is (R_f, R_t) = (2, 1) repeated. We confirmed that we can send high data over long distances in the South Sea.

• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.732-739
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• 2009

Flow phantom with stenosis was manufactured using an auto-injector to obtain angiostenotic flow information and quality assurance (QA) for ultrasound diagnostic instrumentation. Effectiveness of manufactured flow phantom with stenosis was investigated with power Doppler that was known to have diagnostic efficiency for angiostenosis. The flow phantom with stenosis was manufactured to 70% stenosis with 8 mm and 2.4 mm silicon tube, and silicone tube was covered with gelatin that has acoustic characteristics similar to soft tissue. When the linear transducer was used for measurement, the estimated diameter of normal vessel was measured lower than that of normal value, and the estimated diameter of stenosed vessel was measured higher than that of normal value. The measured parameters were not affected except for the radical conditions such as gain of 60%, PRF of 3000 Hz, use of maximal filter or angle. In addition, when the convex transducer was used for measurement, measurement parameters were affected by gain, PRF, filter, and angle. Therefore it is expected that flow phantom with stenosis manufactured with an auto-injector will be utilized effectively for QA of angiostenotic diagnosis.