• Journal for History of Mathematics
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• v.21 no.1
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• pp.97-108
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• 2008

In this paper, we investigate the analytic Feynman integral, the analytic Fourier-Feynman transform and convolution product on Wiener space. We then consider various results between these concepts.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.4
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• pp.403-413
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• 2007

As rock bolts become one of the main support systems in tunnels and underground structures, the integrity of the rock bolts affects the safety of these types of structures. The purpose of this study is the evaluation of rock bolt integrity using Fourier and wavelet transforms of the guided ultrasonic waves. After five rock bolt specimens with various defect ratios are embedded into a large scale concrete block, guided waves are generated by a PZT (lead zirconate titanate) element and measured by an acoustic emission (AE) sensor. The captured signals are analyzed in the frequency domain using the Fourier transform, and in the time-frequency domain using the wavelet transform based on a Gabor wavelet. The spectrum obtained from the Fourier transform shows that a portion of high frequency contents increases with increase in the defect ratio. Peak values in the time-frequency domain represent the interval of travel time of each echo. The energy velocities of the guided waves increase with the defect ratio. This study shows that the spectrum ratio and the energy velocity may be indicators fur the evaluation of rock bolt integrity.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10d
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• pp.580-582
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• 2002

본 논문은 위상한정상관법을 이용하여 겹쳐진 화상이 둘 중 어떤 화상에 더 유사한 지를 정량적으로 측정하는 알고리듬을 제안한다. 제안된 알고리듬은 화상을 푸리에변환하여 위상만을 가지고 합성화상을 만든 다음 역푸리에변환을 통하여 만들어지는 위상한정상관을 가지고 유사도를 측정한다. 본 알고리듬에서는 유사도를 충분히 구분할 수 있을 정도로 상수로 설정된 진폭을 충분히 크게 하고 중심부분이외에 나타나는 피크치를 무시하고 오직 중심부분 만의 피크치를 원화상의 자기상관과 비교한다. 실험결과는 진폭을 100으로 하였을 경우 위상한정상관의 피크는 그 유사도가 1에서 0까지 변함에 따라서 100에서 40까지변하는 것을 보여 준다. 이것은 제안된 알고리듬이 위상한정상관을 이용하여 화상의 유사도를 정량적으로 효과적으로 측정하는데 사용될 수 있음을 보여준다.

• 한국지구물리탐사학회:학술대회논문집
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• 2011.10a
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• pp.177-178
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• 2011

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.3
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• pp.34-40
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• 2002

In this paper, a new encryption method for a binary image using Phase modulation and Fourier transform is proposed. For decryption we use the characteristics of square law detector. In encryption process, a key image is obtained by phase modulation of 256 level random pattern and its Fourier transformation, and input image is encrypted by Fourier transforming the multiplication of the phase modulated random pattern and phase modulated input image. The encrypted image and key image have only phase information, so they can not be copied or counterfeited and the original image can not be decrypted without the key image. To reconstruct the original image, each phase mask of the key image and the encrypted image must be placed on each path of the Mach-Zehnder interferometry with Fourier transform lens and the output image is obtained in the form of intensity in the CCD(Charge Coupled Device) camera. The real-time decryption is possible in the proposed system by use of a LCD as a phase modulator and a CCD camera as an intensity detector. The proposed method shows a good performance in the computer simulation and optical experiment as an encryption scheme.

• Korean Journal of Optics and Photonics
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• v.21 no.3
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• pp.91-96
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• 2010

The size of a reconstructed image depends on the reconstruction distance and wavelength. The double fourier transform method is proposed to eliminate the dependence on the reconstruction distance and wavelength. We can get a fixed reconstructed image size by using the double fourier transform method. Two wavelength digital holography is proposed to measure the step height, which is larger than a single wavelength. The two image size of different wavelength holograms should be the same in order to apply two wavelength digital holography. We use two wavelength digital holography and double fourier transforms to measure the step height. The measured data were reasonable and we found that the double fourier transform is useful in two wavelength digital holography.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.2
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• pp.237-242
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• 2011

This paper proposes a detection algorithm for each section which detects the voiced section, unvoiced section, and the silence section at each frame using a multi-layer perceptron neural network. First, a power spectrum and FFT (fast Fourier transform) coefficients obtained by FFT are used as the input to the neural network for each frame, then the neural network is trained using these power spectrum and FFT coefficients. In this experiment, the performance of the proposed algorithm for detection of the voiced section, unvoiced section, and silence section was evaluated based on the detection rates using various speeches, which are degraded by white noise and used as the input data of the neural network. In this experiment, the detection rates were 92% or more for such speech and white noise when training data and evaluation data were the different.

• Korean Journal of Optics and Photonics
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• v.27 no.3
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• pp.101-105
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• 2016

In this study we propose the novel optimization method of the phase-only computer-generated hologram (CGH), to improve calculation speed compared to the conventional method. While the conventional method is calculated using numerical analysis, the novel method is calculated using the phase-shift characteristic of Fourier transformation. In addition, the selectivity of noise filtering lets it decrease the calculation time. The validity of the reconstructed image using the novel method is verified by comparing simulation results to ideal and conventional data, and the improvement of texture and sharpness of the reconstructed image is confirmed by simulation.

• Journal of KIISE
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• v.42 no.4
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• pp.483-486
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• 2015

Security systems that use face recognition are vulnerable to spoofing attacks where unauthorized individuals use a photo or video of authorized users. In this work, we propose a method to detect a face spoofing attack with a video of an authorized person. The proposed method uses three sequential frames in the video to extract features by using Fourier Transform and Dense-SIFT filter. Then, classification is completed with a Support Vector Machine (SVM). Experimental results with a database of 200 valid and 200 spoof video clips showed 99% detection accuracy. The proposed method uses simplified features that require fewer memory and computational overhead while showing a high spoofing detection accuracy.

• The Journal of the Korea Contents Association
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• v.13 no.10
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• pp.1-8
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• 2013

In this paper, we propose a new method to correct the perspective distortion that occurs in the process of acquiring the integral images. In the proposed method, the distortion correction is based on the spectral characteristics of integral images. As element images of an integral image are repeated nearly periodically, its Fourier spectrum is given as an impulse train. On the contrary, the impulse train do not appear in the spectra of distorted images. In the proposed method, therefore, the perspective distortion parameters are detected by using the characteristics of the spectrum obtained through the Fourier transform, and then the distorted images are corrected by using the parameters. Through experiments, we verify that the proposed method effectively works for the perspective distortion correction.