• The Journal of the Acoustical Society of Korea
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• v.40 no.5
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• pp.473-478
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• 2021

Vibrato corresponds to a modulation of frequency and is one of the most frequently used techniques to enrich vocal and musical instrument sounds. Whereas the fundamental frequency trajectories of vibrato tones are generally modeled as a sinusoid, they are sometimes observed to be non-sinusoidal. In this paper, we propose a method to analyze the characteristics of non-sinusoidal fundamental frequency trajectories of vibrato sounds. The proposed method performs Fast Fourier Transform (FFT)-based harmonic analysis on the frequency trajectory, analyzes vibrato parameters, and calculates a sinusoid purity factor. We applied the proposed method to flute, viola, and saxophone vibrato tones, whose results showed the effectiveness of the proposed method.

• Journal of IKEEE
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• v.23 no.2
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• pp.614-621
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• 2019

In this paper, we presents the integral equation-fast Fourier transform(IE-FFT) and block matrix preconditioner (BMP) to solve electromagnetic scattering problems of penetrable structures composed of dielectric or magnetic materials. IE-FFT can significantly improve the amount of calculation to solve the matrix equation constructed from the moment method(MoM). Moreover, the iterative method in conjunction with BMP can be significantly reduce the number of iterations required to solve the matrix equations which are constructed from electrically large structures. Numerical results show that IE-FFT and block matrix preconditioner can solve electromagnetic scattering problems for penetrable objects quickly and accurately.

• Journal of electromagnetic engineering and science
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• v.19 no.1
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• pp.6-12
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• 2019

An IE-FFT algorithm is implemented and applied to the electromagnetic (EM) solution of perfect electric conducting (PEC) scattering problems. The solution of the method of moments (MoM), based on the magnetic field integral equation (MFIE), is obtained for PEC objects with closed surfaces. The IE-FFT algorithm uses a uniform Cartesian grid to apply a global fast Fourier transform (FFT), which leads to significantly reduce memory requirement and speed up CPU with an iterative solver. The IE-FFT algorithm utilizes two discretizations, one for the unknown induced surface current on the planar triangular patches of 3D arbitrary geometries and the other on a uniform Cartesian grid for interpolating the free-space Green's function. The uniform interpolation of the Green's functions allows for a global FFT for far-field interaction terms, and the near-field interaction terms should be adequately corrected. A 3D block-Toeplitz structure for the Lagrangian interpolation of the Green's function is proposed. The MFIE formulation with the IE-FFT algorithm, without the help of a preconditioner, is converged in certain iterations with a generalized minimal residual (GMRES) method. The complexity of the IE-FFT is found to be approximately $O(N^{1.5})$and $O(N^{1.5}logN)$ for memory requirements and CPU time, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.439-441
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• 2019

Deep learning has become a powerful and robust algorithm in Artificial Intelligence. One of the most impressive forms of Deep learning tools is that of the Convolutional Neural Networks (CNN). CNN is a state-of-the-art solution for object recognition. For instance when we utilize CNN with MNIST handwritten digital dataset, mostly the result is well. Because, in MNIST dataset, all digits are centralized. Unfortunately, the real world is different from our imagination. If digits are shifted from the center, it becomes a big issue for CNN to recognize and provide result like before. To solve that issue, we have created frequency images from spatial images by a Fast Fourier Transform (FFT).

• Journal of the Architectural Institute of Korea Planning & Design
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• v.36 no.4
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• pp.41-49
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• 2020

The purpose of this study was to investigate the use of the Deep Neural Networks(DNN) model to classify user's emotions, in particular Electroencephalography(EEG) toward Virtual-Reality(VR) based 3D design alternatives. Four different types of VR Space were constructed to measure a user's emotion and EEG was measured for each stimulus. In addition to the quantitative evaluation based on EEG data, a questionnaire was conducted to qualitatively check whether there is a difference between VR stimuli. As a result, there is a significant difference between plan types according to the normalized ranking method. Therefore, the value of the subjective questionnaire was used as labeling data and collected EEG data was used for a feature value in the DNN model. Google TensorFlow was used to build and train the model. The accuracy of the developed model was 98.9%, which is higher than in previous studies. This indicates that there is a possibility of VR and Fast Fourier Transform(FFT) processing would affect the accuracy of the model, which means that it is possible to classify a user's emotions toward VR based 3D design alternatives by measuring the EEG with this model.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.3
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• pp.272-276
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• 2005

This paper deals with the method to calculate the rotor eddy current losses of permanent magnet high-speed machines considering the effects of time/space flux harmonics. The flux harmonics caused by the slot geometry in the stator is calculated from the time variation of the magnetic field distribution obtained by the magneto-static finite element analysis and double Fast Fourier Transform. And, using the analytical approach considering the multiple flux harmonics and the Poynting vector, the rotor losses is evaluated in each rotor composite. Using this method is simple and workable for any kind of stator slot shape for rotor loss analysis.

• Journal of the Optical Society of Korea
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• v.19 no.2
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• pp.165-168
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• 2015

A simple method to determine the focal length of a lens using the Talbot image is presented. This method uses only one grating, requiring neither Moir$\acute{e}$ fringe analysis nor the angle between the gratings. The original Fourier transform was used to access the spectrum beyond the limitation set of the usual fast Fourier transform to determine the (de)magnification accurately enough to be used for the focal length. A set of Talbot images simulated numerically with the Fresnel diffraction integral was used to demonstrate the method. For focal lengths between 5550 mm and 5650 mm, the mean difference between the focal lengths determined from the Talbot images and the true values was 3.3 mm with the standard deviation of the difference being 3.8 mm. The true focal lengths can be recovered with an accuracy of 0.06%.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.10-12
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• 2002

최근에 많은 새로운 타입의 어플리케이션에서 정보 시스템들에 대한 사용의 증가로 인해 연속 질의들은 여러 연구 프로젝트들에서 초점이 되고 있으며 연구가 활발히 진행되고 있다. 특히 시계열에 대해서 미래의 값에 대한 예측 모델과 FFT(Fast Fourier Transform)을 이용하여 새로운 값이 입력될 때마다 신속하게 응답할 수 있는 이웃에 관한 연속 질의에 대해 이미 연구되었다. 그러나 이것은 이웃에 관한 질의이며 또한 방대한 데이터를 처리함에 있어서 매우 효율적이지 못하다. 이 논문에서는 시계열에 있어서 예측 모델을 이용하여 미래의 값을 예측한다. 다음 DFT(Discrete Fourier Transform)을 이용하여 변환한 후 R*-tree를 구성하고, 새로운 값이 입력될 때마다 신속하게 유사성 시계열들을 찾아서 응답하는 연속 범위 질의 과정과 시스템 구조에 대해 제안한다.

• Journal of the Optical Society of Korea
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• v.12 no.4
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• pp.281-287
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• 2008

An acousto-optic tunable filter based 3-D micro surface profile measurement using an equally spaced 5 spectral phase shifting is described. The 5-bucket spectral phase shifting method is compared with a Fourier-transform method in the spectral domain. It can provide a fast measurement capability while maintaining high accuracy since it needs only 5 pieces of spectrally phase shifted imaging data and a simple calculation in comparison with the Fourier transform method that requires full wavelength scanning data and relatively complicated computation. The 3-D profile data of micro objects can be obtained in a few seconds with an accuracy of ${\sim}10nm$. The 3-D profile method also has an inherent benefit in terms of being speckle-free in measuring diffuse micro objects by employing an incoherent light source. Those simplicity and practical applicability is expected to have diverse applications in 3-D micro profilometry such as semiconductors and micro-biology.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.2
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• pp.196-200
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• 1987

The following methods are proposed for implementing digital dual tone multi-frequency (DTMF) receiver: using infinite impulse response(IIR) digital filters, period-counting algorithm, discrete Fourier transform(DFT), and fast Fourier transform(FFT)[2]. The PARCOR(Partical Correlation) analysis method which has been widly used in the speech signal processing area is applied to the dual tone multi-frequency(DTMF) signal detection. This method is easy to implement digitally and stronger to digit simulation of speech than any other methods proposed up to date. Since sampling rate of 4KHz is used in the DTMF receiver for the detection of input DTMF signal originally sampled at 8KHz, it effects two times higher multiplexing efficiency.