• 음성과학
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• 제8권4호
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• pp.35-43
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• 2001

New speech synthesis algorithms capable of flexible prosody (especially F0) modification are desired for a high quality TTS system. TD-PSOLA is the most popular synthesis algorithm. The algorithm shows very high quality when F0 modification is limited. However, the quality degradation due to pitch epoch detection error becomes severe as the F0 modification factor becomes large. On the other hand, the vocoder framework is very flexible in F0 manipulation. The synthesized speech quality from the vocoder is far from natural human speech and suffers from buzziness. To remedy the buzzy quality from the vocoder and make more natural synthetic speech, we propose a mixed phase vocoder.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2002년도 춘계학술발표논문집 (상)
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• pp.209-212
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• 2002

본 논문은 손실 압축(lossy compression)에 강인한 오디오 워터마킹(audio watermarking) 기술을 제안한다. 제안된 워터마킹 기술은 온라인으로 유통되고 있는 MP3, AAC, WMA, RA, ATRAC 등과 같은 대부분의 오디오 압축 포멧으로 변형되더라도 삽입된 정보를 검출할 수 있다. 실험 결과 BER 이 9% 이내로 오류 정정 코드 (error correction code)를 이용해서 삽입 정보를 100% 검출 가능하였다.

• 한국공작기계학회논문집
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• 제14권6호
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• pp.68-73
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• 2005

Tire manufactures have dealt with noise problem by varying the pitch of the tread. The various formulas for the variations are generally determined differently, however. Often these variations are based on a combination of trial and error, intuition, and economics. Some manufactures have models and analogs to test tread patterns and their variations. These efforts, however practical, do not determine the best variation beforehand or guarantee the best results. For this reason it was felt that a general mathematical approach fur determining the best variation was needed. Moreover, the method should be completely general, easy to use, and sufficiently accurate. This paper discusses a mathematical method called Mechanical Frequency Modulation(MFM) which meets the above requirements. Thus, MFM pertains to computing an irregular time sequence of events so that the resulting excitation spectrum is shaped to a preferred form. The first part of this paper treats the theoretical basis for computing an optimum variation ; the second part discusses experimental results and simulation program which corroborate the theory.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권2호
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• pp.149-159
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• 2017

In this study, the numerical investigation of ship motions and added resistance at constant forward velocity of KVLCC2 model is presented. Finite volume CFD code is used to calculate three dimensional, incompressible, unsteady RANS equations. Numerical computations show that reliable numerical results can be obtained in head waves. In the numerical analyses, body attached mesh method is used to simulate the ship motions. Free surface is simulated by using VOF method. The relationship between the turbulence viscosity and the velocities are obtained through the standard ${\kappa}-{\varepsilon}$ turbulence model. The numerical results are examined in terms of ship resistance, ship motions and added resistance. The validation studies are carried out by comparing the present results obtained for the KVLCC2 hull from the literature. It is shown that, ship resistance, pitch and heave motions in regular head waves can be estimated accurately, although, added resistance can be predicted with some error.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권2호
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• pp.28-33
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• 2001

The subject of this study is to improve the position performance of the linear motion for hybrid type Linear Pulse Motor (HLPM). Generally, there are two applicable methods to ensure precise position control ; a good processing method. This paper is suggested an electrical 125 microstep driving method so as to achieves the excellent control performance, besides the small mechanical manufacture of teeth pitch. The compensation method of digital PI control is apply to step response of stable position control, step error, vibration suppression and the approach to high stability, and the Ziegler-Nichols tuning method is applied to the proper design of control parameter. The proposed control method has been verified by simulation results of the suitable gain and phase margin of bode plot, and from experiment result of step response.

• 한국자기학회지
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• 제5권5호
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• pp.650-654
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• 1995

In digital video recording, higher areal density is strongly required for realizing digital VCRs. In order to accomplish higher areal density. we have implemented a system that has a narrow track pitch and can record data of about 30 Mbps(15 Mbps per channel) with the conventional S-VHS tapes. After computer simulation using the characteristics of the experimental system, we have selected appropriate equalizer and detection method by taking into account performance and cost (including hardware complexity). As a result, the selected equalizer and detection schemes are cosine equalizer and integrated de tection, respectively. The implemented system confirms reliable operation with a symbol error rate of less than $1{\times}10^{-4}$. In this paper, We will show the performance of the implemented system together with simulation results.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2009년도 춘계학술발표대회
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• pp.63-66
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• 2009

사람의 감정 변화에는 크게 기쁨, 슬픔, 흥분, 보통 4가지 상태로 말할 수 있다. 이 4가지 상태에서 기쁨과 슬픔, 흥분과 기쁨 상태가 음성학적으로 비슷한 형태를 가지고 있다. 흥분과 기쁨의 상태에서 방언의 노말 상태가 표준어의 기쁨, 흥분상태와 비슷한 특징을 가지고 있다. 이와 같은 표준어와 방언 간의 특징 때문에 흥분 상태를 인지하는 경우 방언의 보통상태가 흥분상태로 잘못 인식되는 경우가 발생 한다. 본 논문에서는 이와 같은 문제점이 발생하는 음성학적인 차이를 구분 하고자 한다. 이들을 비교하기 위해 Pitch, Formant와 Formant RMS error 3가지 요소를 통하여 표준어와 방언간의 흥분 상태를 연구 하였다.

• 풍력에너지저널
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• 제4권2호
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• pp.17-24
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• 2013

Idealized PID-controlled rotor-speed error for blade pitch control of wind turbines responds as a second-order system with natural frequency and damping ratio for closed-loop system. RISO National Laboratory has recommended specific natural frequency(=0.6 rad/s) and damping ratio(=0.7) for 2 MW wind turbine. The baseline controller for 5 MW wind turbine of NREL(National Renewable Energy Laboratory) is designed based on the same values of RISO recommendation. This study investigates the effect of the natural frequency and damping ratio of the controller for NREL 5 MW wind turbine. It is confirmed that RISO recommendation shall be tuned for each wind turbine.

• 한국정밀공학회지
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• 제22권11호
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• pp.135-141
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• 2005

Measurement of five DOF motion errors in a ultra precision feed table was attempted in this study. Yaw and pitch error were measured by using a laser interferometer and roll error was measured by using the reversal method. Linear motion errors in the vertical and horizontal directions were measured by using the sequential two point method. In this case, influence of angular motion errors was compensated by using the previously measured ones by the laser interferometer and the reversal method. The capacitive type sensors and an optical straight edge were used in the reversal method and the sequential two point method. Influence of thermal deformation on sensor jig was investgated and minimized by the periodic measurement according to the variation of room temperature. Deviation of gain between sensors was also compensated using the step response data. 5 DOF motion errors of a hydrostatic table driven by the linear motor werer tested using the measurement method. In the horizontal direction, measuring accuracies for the linear and angular motion were within ${\pm}0.02\;{\mu}m$ and ${\pm}0.04$ arcsec, respectively. In the vertical direction, they were within ${\pm}0.02{\mu}m$ and ${\pm}0.05$ arcsec. From these results, it was found that the introduced measurement method was very effective to measure 5 DOF motion errors of the ultra precision feed tables.

• 한국음향학회지
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• 제15권6호
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• pp.59-65
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• 1996

본 논문에서는 기존의 4.8 kbps VSELP에 상응하는 음질을 갖는 4 kbps PSI-VSELP(Pitch Synchrononus Innovation-Vector Sum Excited Linear Prediction) 음성 부호화기를 제안한다. 'Half-rate'는 4kbps 내외에서 지역에 따라 다소 차이가 있으므로 기존의 half-rate 부호화기를 사용하기 위해서는 비트율을 감소시킬 필요가 생긴다. 이때, 비트율 감소에 따른 성능저하를 최소화하기 위해서는 전송 변수가 부호화기의 성능에 미치는 영향을 고려하여 비트 할당을 결정하는 것이 바람직하다. 본 논문에서는 이러한 접근 방식으로 비트율 감소 연구를 수행한 후, 제안된 부호화기에 대한 4 kbps 비트 할당을 결정한다. VSELP 부호화기의 음질 향상을 위해서, 성능에 가장 중요한 영향을 미치는 기저 벡터는 반복 폐회로 훈련 과정을 통해 최적화하며, PSI 기법을 VSELP 부호화기에 도입한다. 제안된 음성 부호화기의 성능을 평가하기 위해 배경 잡음과 채널 에러가 없는 환경에서 실험을 하였다. 실험 결과, 제안된 4 kbps PSI-VSELP는 4.8 kbps VSELP에 비해 객관적 음질은 낮았지만, 주과적 음질은 더 높게 나타났다.