• 말소리와 음성과학
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• 제6권4호
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• pp.133-139
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• 2014

This paper describes several approaches to transform a speaker's individuality to another's individuality using frequency warping between bilingual formant frequencies on different language environments. The proposed methods are simple and intuitive voice conversion algorithms that do not use training data between different languages. The approaches find the warping function from source speaker's frequency to target speaker's frequency on formant space. The formant space comprises four representative monophthongs for each language. The warping functions can be represented by piecewise linear equations, inverse matrix. The used features are pure frequency components including magnitudes, phases, and line spectral frequencies (LSF). The experiments show that the LSF-based voice conversion methods give better performance than other methods.

• 한국정보통신학회논문지
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• 제7권7호
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• pp.1380-1386
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• 2003

화자들 사이의 성도의 길이의 변이에 의하여 음성 인식기의 성능이 저하된다. 본 연구에서는 입력 음성에서 추출한 단구간 스펙트럼의 주파수축을 확대하거나 축소하여 음성인식기에 미치는 화자사이의 성도 길이의 영향을 최소화하는 방법을 사용한다 성도의 길이를 정규화하기 위한 주파수 변환 함수로서, 선형의 주파수 변환 함수와 조각적 선형적인 변환 함수를 고려하였다. 또한, 커다란 성도길이의 변이에 따른 주파수축의 척도변화를 보다 효과적으로 모의할 수 있는 가변구간 조각적 선형함수를 제안한다. TIDIGITS 연결 숫자음 음성자료에 대하여 제안한 방법을 적용한 결과, 단어의 오인식률을 2.15%에서 0.53%로 크게 감소시킴으로서, 성도 길이 정규화가 화자 독립 음성인식기의 성능 향상에 필수적임을 알 수 있었다.

• 한국지능시스템학회논문지
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• 제11권7호
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• pp.628-632
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• 2001

We propose time-frequency (TF) tools for analyzing linear time-varying (LTV) systems and nonstationary random processes. Obtained warping the narrowband Weyl symbol (WS) and spreading function (SF), the new TF tools are useful for analyzing LTV systems and random processes characterized by generalized frequency shifts, This new Weyl symbol (WS) is useful in wideband signal analysis. We also propose WS an tools for analyzing systems which produce dispersive frequency shifts on the signal. We obtain these generalized, frequency-shift covariant WS by warping conventional, narrowband WS. Using the new, generalized WS, we provide a formulation for the Weyl correspondence for linear systems with instantaneous of linear signal transformation as weighted superpositions of non-linear frequency shifts on the signal. Application examples in signal and detection demonstrate the advantages of our new results.

• 한국지능시스템학회논문지
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• 제11권6호
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• pp.563-567
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• 2001

We generalize the widebane P0-weyl symbol (P0WS) and the widebane spreading function (WSF) using the generalized warping function . The new generalized P0WS and WSF are useful for analyzing system and communication channels producing generalized time shifts. We also investigated the relationship between the affine Wey1 symbol(AWS) and the P0WS. By using specific warping functions, we derive new P0WS and WSF as analysis tools for systems and communication channels with non-linear group delary characteristics. The new P0WS preserves specific types of changes imposed on random processes. The new WSF provides a new interpretation of output of system and communication channel as weighted superpositions of non-linear time shifts on the input. It is compared to the conventional method obtaining output of system and communication channel as a convention integration of the input with the impulse response of the system and the communication channel. The convolution integration can be interpreted as weighted superpositions of liner time shifts on the input where the weight is the impulse response of the system and the communication channel. Application examples in analysis and detection demonstrate the advantages of our new results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.130-135
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• 2011

A study of the bending-extension-transverse shear coupled random response of the composite beams with thin-walled open sections subjected to various types of concentrated and distributed random excitations is dealt with in this paper. First of all, equations of motion of thin-walled composite H-type cross-section beams incorporating a number of nonclassical effects of transverse shear and primary and secondary warping, and anisotropy of constituent materials are derived. On the basis of derived equations of motion, analytical expressions for the displacement response of the composite beams are derived by using normal mode method combined with frequency response function method.

• 대한조선학회논문집
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• 제40권4호
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• pp.16-21
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• 2003

The very large container ships have been built recently and those ships have very small structural rigidity compared with the other conventional ships. As a result, the destruction of ship hull is occurred by the springing including to warping phenomena due to encounter waves. In this study, the solutions of hydrodynamic coefficients are obtained by solving the three dimensional source distribution method and the forward speed Green function representing a translating and pulsating source potential for infinite water depth is used to calculating the integral equation. The vessel is longitudinally divided into various sections and the added mass, wave damping and wave exciting forces of each section is calculated by integrating the dynamic pressures over the mean wetted section surface. The equations for six degree freedom of motions is obtained for each section in the frequency domain and stiffness matrix is calculated by Euler beam theory. The computations are carried out for very large ship and effects of bending and torsional ridigity on the wave frequency and angle are investigated.

• The Journal of the Acoustical Society of Korea
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• 제22권1E호
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• pp.26-32
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• 2003

We propose new time-frequency (TF) tools for analyzing linear time-varying (LTV) systems and nonstationary random processes showing hyperbolic TF structure. Obtained through hyperbolic warping the narrowband Weyl symbol (WS) and spreading function (SF) in frequency, the new TF tools are useful for analyzing LTV systems and random processes characterized by hyperbolic time shifts. This new TF symbol, called the hyperbolic WS, satisfies the hyperbolic time-shift covariance and scale covariance properties, and is useful in wideband signal analysis. Using the new, hyperbolic time-shift covariant WS and 2-D TF kernels, we provide a formulation for the hyperbolic time-shift covariant TF symbols, which are 2-D smoothed versions of the hyperbolic WS. We also propose a new interpretation of linear signal transformations as weighted superposition of hyperbolic time shifted and scale changed versions of the signal. Application examples in signal analysis and detection demonstrate the advantages of our new results.

• Structural Engineering and Mechanics
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• 제28권4호
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• pp.387-410
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• 2008

The fatigue damage accumulation rates of horizontally curved thin walled box-girder bridge have been estimated from vehicle-induced dynamic stress history using rain flow cycle counting method in the time domain approach. The curved box-girder bridge has been numerically modeled using computationally efficient thin walled box-beam finite elements, which take into account the important structural actions like torsional warping, distortion and distortional warping in addition to the conventional displacement and rotational degrees of freedom. Vehicle model includes heave-pitch-roll degrees of freedom with longitudinal and transverse input to the wheels. The bridge deck unevenness, which is taken as inputs to the vehicle wheels, has been assumed to be a realization of homogeneous random process specified by a power spectral density (PSD) function. The linear damage accumulation theory has been applied to calculate fatigue life. The fatigue life estimated by cycle counting method in time domain has been compared with those found by estimating the PSD of response in frequency domain. The frequency domain method uses an analytical expression involving spectral moment characteristics of stress process. The effects of some of the important parameters on fatigue life of the curved box bridge have been studied.