• The Journal of the Acoustical Society of Korea
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• v.10 no.1
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• pp.20-29
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• 1991

A fundamental assumption in conventional linear predictive coding (LPC) analysis procedure is that the input to an all-pole vocal tract filter is white process. In the case of periodic inputs, however, a pitch bias error is introduced into the conventional LP coefficient. Multi-pulse (MP) LP analysis can reduce this bias, provided that an estimate of the excitation is available. Since the prediction error of conventional LP analysis can be modeled as the sum of an MP excitation sequence and a random noise sequence, we can view extracting MP sequences from the prediction error as a classical detection and estimation problem. In this paper, we propose an algorithm in which the locations and amplitudes of the MP sequences are first obtained by applying a likelihood ratio test (LRT) to the prediction error, and LP coefficients free of pitch bias are then obtained from the MP sequences. To verify the performance enhancement, we iterate the above procedure with adaptive threshold at each step.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.917-921
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• 2000

One of the major limitations of productivity and quality in machining is machining accuracy of the machine tools. The machining accuracy is affected by geometric, volumetric errors of the machine tools. This paper suggests the enhancement method of machining accuracy for precision machining of high quality metal reflection mirror or optics lens, etc. In this paper, we study 1) the compensation of linear pitch error with NC controller compensation function using laser interferometer measurement, 2) the method for enhancing the accuracy of NC milling machining by modeling and compensation of volumetric error, 3) the generation of the parabolic face profile. And the method is verified by the parabolic face machining experiment with a vertical three axes NC milling machine. After this study, we will inspect using On-machine measurement and study the repetitive machining by a compensated path

• Transactions of Materials Processing
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• v.5 no.2
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• pp.115-121
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• 1996

Recently it is attempted to manufacture gears by various cold forging methods to meet requirements of mass production and uniform qualities. Compared to machined gears cold forged ears reveal higher tooth strength and better surface roughness but they reveal lower geometrical accuracies. Therefore in the present study a series of experiments are performed to investigate relations between geometrical accuracies of dies and billet and those of the final product. The geometrical accuracies of forged gears are considered through functional gear-element tolerances by measuring pitch error profile error lead error radial error tooth thickness and rolling test. Results of the experiments can be summarized as follows: (1) involute spur gears of KS 5(or AGMA7) accuracies can be made,(2) concentricity of die set should be maintained within 0.01mm (3) clearance between the billet and die set should be less than 0.1mm (4) con-centricity and radial runout should be less than 0.08mm and 0.1mm respectively. However it is thought that FEM analysis of elastic/thermal deformations of dies and the billet is necessary for a better understanding of the findings obtained through the present study.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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• pp.24-30
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• 2020

The high speed of an engine balance box may cause significant additional gear noise. Gear accuracy is the most useful key to reduce gear noise, but the small tooth width and thin-walled anti-backlash gear introduce challenges to the manufacturing process. In order to reduce the gear noise caused by gear pitch error, this paper investigates the correlation between influencing factors and gear pitch error by analyzing the processing technology, tooling fixture, and equipment accuracy. By improving the process and optimizing the gear design, the gear machining accuracy was improved and the processing cost was saved.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.649-657
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• 1992

Transmission error for a stepping motor-timing belt drive system is investigated experimentally and analytically. From FFT analysis of the experimental results, it is found that the transmission error consists of three periodic errors : (1) error by the stepping motor per one resolution angle theta.$_{m}$, (2) error by the pulley eccentricity per one revolution theta.$_{e}$, and (3) error by the meshing effect between the belt and the pulley teeth per one pitch revoltion theta.$_{p}$. In order to investigate the effects of some design parameters on the transmission error, the dynamic models of the stepping motor-timing belt drive system are derived by Bondgraph. According to the simulation results, as the belt total tension increases, theta.$_{m}$ and theta.$_{e}$ decrease due to the nonlinearity of the belt. In adition, the numerical and experimental results show that theta.$_{m}$ and theta.$_{e}$ of the loaded case are larger than those of the unloaded case. The analytical results are in good accordance with the experimental results.sults.s.sults.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.4
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• pp.371-377
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• 2013

This paper proposes three methods for improving the accuracy of auto-music transcription considering with time-varying tempo from monophonic sound. The first one that uses TV(Total Variation) filter for smoothing the pitch data reduces the fragmentation in the pitch segmentation result. Also, the measure finding method that combines three different ways based on pitch and energy of sound data, respectively as well as based on rules produces more stable result. In addition the temporal result of note-length encoding is corrected in optimal way that the resulted encoding minimizes the sum of quantization error in a measure while the sum of note-lengths is equal to the number of beats. In the experiment with 16 children songs, we obtained the improved result in which measure finding was complete, the accuracy of encoding for note-length and pitch was about 91.3 and 86.7, respectively.

• Korean Journal of Audiology
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• v.25 no.3
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• pp.131-137
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• 2021

Background and Objectives: The current study investigates pitch coding using frequency following response (FFR) among vocalists, violinists, and non-musicians for Indian Carnatic transition music stimuli and assesses whether their listening biographies strengthen their F0 neural encoding for these stimuli. Subjects and Methods: Three participant groups in the age range of 18-45 years were included in the study. The first group of participants consisted of 20 trained Carnatic vocalists, the second group consisted of 13 trained violinists, and the third group consisted of 22 non-musicians. The stimuli consisted of three Indian Carnatic raga notes (/S-R2-G3/), which was sung by a trained vocalist and played by a trained violinist. For the purposes of this study, the two transitions between the notes T1=/S-R2/ and T2=/R2-G3/ were analyzed, and FFRs were recorded binaurally at 80 dB SPL using neuroscan equipment. Results: Overall average responses of the participants were generated. To assess the participants' pitch tracking to the Carnatic music stimuli, stimulus to response correlation (CC), pitch strength (PS), and pitch error (PE) were measured. Results revealed that both the vocalists and violinists had better CC and PS values with lower PE values, as compared to non-musicians, for both vocal and violin T1 and T2 transition stimuli. Between the musician groups, the vocalists were found to perform superiorly to the violinists for both vocal and violin T1 and T2 transition stimuli. Conclusions: Listening biographies strengthened F0 neural coding, with respect to the vocalists for vocal stimulus at the brainstem level. The violinists, on the other hand, did not show such preference.

• Journal of Audiology & Otology
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• v.25 no.3
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• pp.131-137
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• 2021

Background and Objectives: The current study investigates pitch coding using frequency following response (FFR) among vocalists, violinists, and non-musicians for Indian Carnatic transition music stimuli and assesses whether their listening biographies strengthen their F0 neural encoding for these stimuli. Subjects and Methods: Three participant groups in the age range of 18-45 years were included in the study. The first group of participants consisted of 20 trained Carnatic vocalists, the second group consisted of 13 trained violinists, and the third group consisted of 22 non-musicians. The stimuli consisted of three Indian Carnatic raga notes (/S-R2-G3/), which was sung by a trained vocalist and played by a trained violinist. For the purposes of this study, the two transitions between the notes T1=/S-R2/ and T2=/R2-G3/ were analyzed, and FFRs were recorded binaurally at 80 dB SPL using neuroscan equipment. Results: Overall average responses of the participants were generated. To assess the participants' pitch tracking to the Carnatic music stimuli, stimulus to response correlation (CC), pitch strength (PS), and pitch error (PE) were measured. Results revealed that both the vocalists and violinists had better CC and PS values with lower PE values, as compared to non-musicians, for both vocal and violin T1 and T2 transition stimuli. Between the musician groups, the vocalists were found to perform superiorly to the violinists for both vocal and violin T1 and T2 transition stimuli. Conclusions: Listening biographies strengthened F0 neural coding, with respect to the vocalists for vocal stimulus at the brainstem level. The violinists, on the other hand, did not show such preference.

• The Journal of Korean Society for Radiation Therapy
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• v.28 no.2
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• pp.109-121
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• 2016

To verify the accuracy of the image guided radiotherapy using ExacTrac 6D couch, the error values in six directions are randomly assigned and corrected and then the corrected values were compared with CBCT image to check the accurateness of ExacTrac. The therapy coordination values in the Rando head Phantom were moved in the directions of X, Y and Z as the translation group and they were moved in the directions of pitch, roll and yaw as the rotation group. The corrected values were moved in 6 directions with the combined and mutual reactions. The Z corrected value ranges from 1mm to 23mm. In the analysis of errors between CBCT image of the phantom which is corrected with therapy coordinate and 3D/3D matching error value, the rotation group showed higher error value than the translation group. In the distribution of dose for the error value of the therapy coordinate corrected with CBCT, the restricted value of dosage for the normal organs in two groups meet the prescription dose. In terms of PHI and PCI values which are the dose homogeneity of the cancerous tissue, the rotation group showed a little higher in the low dose distribution range. This study is designed to verify the accuracy of ExacTrac 6D couch using CBCT. It showed that in terms of the error value in the simple movement, it showed the comparatively accurate correction capability but in the movement when the angle is put in the couch, it showed the inaccurate correction values. So, if the body of the patient is likely to have a lot of changes in the direction of rotation or there is a lot of errors in the pitch, roll and yaw in ExacTrac correction, it is better to conduct the CBCT guided image to correct the therapy coordinate in order to minimize any side effects.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.3
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• pp.375-383
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• 2008

This paper deals with reduction and analysis of cogging torque for permanent magnet synchronous generators with multi-pole rotor for wind power applications. Open-circuit field solutions are derived using a magnetic vector potential and a two-dimensional (2-d) polar coordinate systems. On the basis of derived open-circuit field solutions and 2-d permeance functions, we also derive open-circuit field solutions considering stator slotting effects. By using open-circuit field solutions considering stator slotting effects and energy variation methods, this paper analytically predicts the cogging torque considering skew effects. All analytical results are shown in good agreement with those obtained from finite element (FE) analyses. In order to reduce the cogging torque, by predicting the variation of the cogging torque according to pole arc/pitch ratio using analytical and FE methods, pole arc/pitch ratio which makes the cogging torque minimum are determined. However, we confirm that measured value for cogging torque of the PMG with determined pole arc/pitch ratio is twice higher than predicted value. Therefore, the reason for an error between measured and predicted cogging torque is discussed in terms of a shape of PMs and is proved experimentally.