• Restorative Dentistry and Endodontics
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• v.31 no.6
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• pp.477-484
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• 2006

The purposes of this study were to compare the apical terminus width of simulated curved root canal prepared with three NiTi file systems used by undergraduates for evaluation the effects of flute angle and pitch or radial land on reducing screw-in effect and to determine more safe NiTi file system for inexperienced operators. Fifty inexperienced undergraduate students prepared 150 simulated curved root canals in resin blocks with three NiTi file systems ; ProFile$^{(R)}$, Hero Shaper$^{(R)}$, K3$^{TM}$. The electric motor set at a speed of 300 rpm and torque of 30 in a 16 : 1 reduction handpiece was used. The simulated root canal was prepared to ISO #25 sizes with each file system. The scanned images of pre- and post-instrumented canal of resin block were superimposed. To evaluate the screw-in effect of three NiTi file systems, apical terminus width of root canal was measured from superimposed images and statistical analysis was performed. There were significant differences in three NiTi flle systems. ProFile$^{(R)}$ had significantly smaller width than Hero Shaper$^{(R)}$ and K3$^{TM}$"" (P < 0.05), but no significant difference was observed between K3$^{TM}$ and Hero Shaper$^{(R)}$. Under the condition of this study, active file system (Hero SHaper$^{(R)}$, K3$^{TM}$) with variable pitch and helical angle had more screw-in effect than passive file system (ProFile$^{(R)}$) with constant pitch and helical angle. It seems that the radial lands play more important role in reducing screw-in effect.

• The Journal of the Acoustical Society of Korea
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• v.14 no.2
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• pp.50-61
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• 1995

A time scale modification method yielding rate-modified speech while conserving the characteristic of speech was implemented in real-time using a goneral purpose digital signal processor. Time scale modification changed pronunciation speed only, producing a time difference between the input signal and the modified signal, making it impossible to implement it in real-time. In this thesis, a system was implemented to remove the time difference between the input and modified signals. Speech signals slowed down or speeded up by a physical time scale modification method, such as adjusting the motor speed of the cassett tape recorder, was used as the input signal. Physical modification that controled only the inter speed of the cassette tape player distorted the pitch period of the original speech. In this study, a real-time system was implemented so that the pitch-distorted speech was reconstructed back to the original by fractional sampling pitch shifting using an FIR filter, and this signal was time scale modified to match the cassette tape recorder motor speed using SOLA time-scale medification. In experiments using speech signals medifiedby the proposed method, results obtained using a 16-bit resolution ADSP2101 processor and using computer simulations employing floating point operations showed about the same average frame signal-to-noise ratio of about 20 dB.

• Journal of Korean Society of Forest Science
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• v.6 no.1
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• pp.37-42
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• 1967

This experiment was carried out to study the peeling effect affecting to the natural seasoning by the treatments such as complete peeling, outer bark peeling (attached inner bark) and non peeling for the logs felled in summer and winter season in the stand of about 40 years old pitch pine, located in Kwangyang College Forest, Chollanam-do, Korea. According to the results this study may be concluded as followings. 1. Although the complete peeled logs are seasoned rapidly as compared with the outer barked and non peeled logs but they are more developed seasonal checking. 2. As to the drying effects of the logs felled in summer season, the difference between complete peeled and outer barked or non peeled logs are recognized. Whereas, the difference between outer barked and non peeled logs was not recognized. 3. As to the drying effects of the test logs felled in winter season the difference between complete peeled and outer barked logs were not shown, whereas, the difference between complete peeled or outer barked, and non peeled logs was significantly recognized. Accordingly it is considered that the drying effect of outer barked logs is same with those of complete peeled logs. 4. In this experiment it is expected that the complete peeled logs of summer season felling, and complete peeled or outer barked logs of winter season felling were attained equilibrium moisture contents within four months.

• Proceedings of the KSPS conference
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• 2006.11a
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• pp.127-130
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• 2006

The purpose of this study is to examine the difference in acoustic features between Young Voices and Aged Voices, which are actually come from the same age group. The 12 female subjects in their thirties were participated and recorded their sustained vowel /a/, connected speech, and reading. Their voices were divided into Younger Voices and Aged Voices, which means voices sound like younger person and sound like in their age or more aged ones. Praat 4.4.22 was used to record and analyze their acoustic features like Fo, SFF, Jitter, Shimmer, HNR, Pitch-range. And the six female listeners guessed the subjects' age and judged whether they sound younger or as like their actual age. We used the Independent t-Test to find the significant difference between those two groups' acoustic features. The result shows a significant difference in Fo, SFF. The above and the previous studies tell us the group who sounds like younger or baby like voice has the similar acoustic features of actually young people.

• Phonetics and Speech Sciences
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• v.11 no.3
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• pp.49-55
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• 2019

This study sought to investigate whether mean speaking fundamental frequency (SFF) can be predicted by parameters of voice and speech range profile (VRP and SRP) in Korean normal adults. Moreover, it explored whether gender differences exist in the absolute differences between the SFF and estimated SFF (ESFF) predicted by the VRP and SRP. A total of 85 native Korean speakers with normal voice participated in the study. Each participant was asked to perform the VRP task using the vowel /a/ and the SRP task using the first sentence of a Korean standard passage "Ga-eul". In addition, the SFF was measured with electroglottography during a passage reading task. Predictive factors of the SFF were explored and the absolute difference between the SFF and the ESFF (DSFF) was compared between gender groups. Results indicated that predictive factors were age, gender, minimum pitch and pitch range for the VRP (adjusted $R^2=.931$), and pitch range (in semi-tones) and maximum pitch for the SRP (adjusted $R^2=.963$), respectively. The SFF and ESFF predicted by the VRP and SRP showed a strong positive correlation. The DSFF of the VRP and SRP, as well as their sum did not differ by gender. In conclusion, the SFF during a passage reading task could be successfully predicted by the parameters of the VRP and SRP tasks. In further studies, clinical implications need to be explored in patients who may exhibit deviations in SFF.

• Journal of the Korean Society of Radiology
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• v.17 no.6
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• pp.801-808
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• 2023

In order to minimize radiation exposure and secure diagnostic value images during CT examination of the head of children, the usefulness of volume axial mode is evaluated through comparison and analysis of exposure dose and images of volume axial mode, high pitch mode, and helical mode. Image evaluation and dose evaluation were performed in CT high pitch mode, helical mode, and volume axial mode for infants under the age of 1 according to the voltages of 70, 80, and 100 kVp tubes. The image evaluation was conducted by comparing image quality by setting ROI for each image, calculating SNR and CNR, using ONE-WAY (ANOVA) to evaluated statistical significance, and cross-examining the dose evaluation using DLP values displayed in the Dose Report. When inspected using volume axial mode, DLP values were generally low, and SNR and CNR values differed by ROI and kVp. When volume axial mode evaluated the quality of the image compared to other scan modes, the difference is not uniform. For the reason, certain modes are not considered excellent, but the exposure dose was reduced the most in terms of dose. In addition, the point that the volume axial mode can be examined at its original location, short scanning time and needless of table movement is useful for CT tests for children under 1 year of age with high radiation sensitivity.

• Phonetics and Speech Sciences
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• v.12 no.4
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• pp.27-36
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• 2020

The aim of this study is to investigate the perceptive aspects of the polysemic sentence final ending "-(eu)lgeol" produced by Chinese Korean learners. "-(Eu)lgeol" has two different meanings, that is, a guess and a regret, and these different meanings are expressed by the different prosodic features of the last syllable of "-(eu)lgeol". To examine how Korean native speakers perceive "-(eu)lgeol" sentences produced by Chinese Korean learners and the most saliant prosodic variable for the semantic discrimination of "-(eu)lgeol" at the perceptive level, we performed a perceptual experiment. The analysed material constituted four Korean sentences containing "-(eu)lgeol" in which two sentences expressed guesses and the other two expressed regret. Twenty-five Korean native speakers participated in the perceptual experiment. Participants were asked to mark whether "-(eu)lgeol" sentences they listened to were (1) definitely regrets, (2) probably regrets, (3) ambiguous, (4) probably guesses, or (5) definitely guesses based on the prosodic features of the last syllable of "-(eu)lgeol". The analysed prosodic variables were sentence boundary tones, slopes of boundary tones, pitch difference between sentence-final and penultimate syllables, and pitch levels of boundary tones. The results show that all the analysed prosodic variables are significantly correlated with the semantic discrimination of "-(eu)lgeol" and among these prosodic variables, the most salient role in the semantic discrimination of "-(eu)lgeol" is pitch difference between sentence-final syllable and penultimate syllable.

• Korean Journal of Radiology
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• v.22 no.11
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• pp.1777-1785
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• 2021

Objective: To investigate the accuracy of the Agatston score obtained with the ultra-high-pitch (UHP) acquisition mode using tin-filter spectral shaping (Sn150 kVp) and a kVp-independent reconstruction algorithm to reduce the radiation dose. Materials and Methods: This prospective study included 114 patients (mean ± standard deviation, 60.3 ± 9.8 years; 74 male) who underwent a standard 120 kVp scan and an additional UHP Sn150 kVp scan for coronary artery calcification scoring (CACS). These two datasets were reconstructed using a standard reconstruction algorithm (120 kVp + Qr36d, protocol A; Sn150 kVp + Qr36d, protocol B). In addition, the Sn150 kVp dataset was reconstructed using a kVp-independent reconstruction algorithm (Sn150 kVp + Sa36d, protocol C). The Agatston scores for protocols A and B, as well as protocols A and C, were compared. The agreement between the scores was assessed using the intraclass correlation coefficient (ICC) and the Bland-Altman plot. The radiation doses for the 120 kVp and UHP Sn150 kVp acquisition modes were also compared. Results: No significant difference was observed in the Agatston score for protocols A (median, 63.05; interquartile range [IQR], 0-232.28) and C (median, 60.25; IQR, 0-195.20) (p = 0.060). The mean difference in the Agatston score for protocols A and C was relatively small (-7.82) and with the limits of agreement from -65.20 to 49.56 (ICC = 0.997). The Agatston score for protocol B (median, 34.85; IQR, 0-120.73) was significantly underestimated compared with that for protocol A (p < 0.001). The UHP Sn150 kVp mode facilitated an effective radiation dose reduction by approximately 30% (0.58 vs. 0.82 mSv, p < 0.001) from that associated with the standard 120 kVp mode. Conclusion: The Agatston scores for CACS with the UHP Sn150 kVp mode with a kVp-independent reconstruction algorithm and the standard 120 kVp demonstrated excellent agreement with a small mean difference and narrow agreement limits. The UHP Sn150 kVp mode allowed a significant reduction in the radiation dose.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1442-1445
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• 2007

Just noticeable differences (jnds) of autocorrelation function (ACF) parameters - Phi (0), Tau 1 and Phi 1 - of household refrigerator noise were investigated by psychoacoustical analyses. Phi (0) of five refrigerators' noise was changed with equal (${\pm}$) interval level of 0.5-1.0 dB up to five intervals by manipulating sound pressure level of the noise. Tau 1 and Phi 1 were varied with equal (${\pm}$) interval of around 0.10 ms and 0.02, respectively. Pitch shifting and strengthen methods were applied for the Tau 1 and Phi 1 variations. As results of subjective evaluations, about 2.0 dB was shown as jnd of Phi (0). The values of 0.30 ms and 0.06 were found as jnds of Tau 1 and Phi 1, respectively. The jnd results of each ACF parameter can be applied to explain substantial amount of sound quality (SQ) enhancement in the SQ prediction indices which were proposed in the authors' previous study [Sato et al. (2007) J. Acoust. Soc. Am.].

• ETRI Journal
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• v.33 no.1
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• pp.99-109
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• 2011

This paper concerns a robust real-time voice activity detection (VAD) approach which is easy to understand and implement. The proposed approach employs several short-term speech/nonspeech discriminating features in a voting paradigm to achieve a reliable performance in different environments. This paper mainly focuses on the performance improvement of a recently proposed approach which uses spectral peak valley difference (SPVD) as a feature for silence detection. The main issue of this paper is to apply a set of features with SPVD to improve the VAD robustness. The proposed approach uses a weighted voting scheme in order to take the discriminative power of the employed feature set into account. The experiments show that the proposed approach is more robust than the baseline approach from different points of view, including channel distortion and threshold selection. The proposed approach is also compared with some other VAD techniques for better confirmation of its achievements. Using the proposed weighted voting approach, the average VAD performance is increased to 89.29% for 5 different noise types and 8 SNR levels. The resulting performance is 13.79% higher than the approach based only on SPVD and even 2.25% higher than the not-weighted voting scheme.