• 대한한의학회지
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• 제32권4호
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• pp.139-148
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• 2011

Objective: The purpose of this study was to investigate the effect of food intake on the Fourier components of radial pulse wave. Methods: Thirty-one healthy male subjects participated in this study. Radial pulse was measured using 3 dimensional pulse imaging system (DMP-3000) before, right after, 40 minutes after, 80 minutes after and 120 minutes after food intake. Fourier transform was performed and the frequency and amplitude of Fourier components were analyzed. Results: 1. The frequency and the amplitude of Fourier components of radial pulse wave increased significantly after food intake. 2. The frequency of Fourier components increased right after food intake and then gradually decreased as time passed, however the amplitude of Fourier components increased and maintained certain levels and patterns throughout the experimental period of 120 minutes. 3. The change ratios of the frequency and the amplitude of Fourier components after food intake varied with the pulse measuring locations. Conclusions: Food intake exerts an influence on radial pulse wave, resulting in increase of frequency and amplitude of Fourier components. The change ratios of the frequency and the amplitude of Fourier components after food intake varied with the pulse measuring locations.

• 대한예방한의학회지
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• 제3권1호
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• pp.173-179
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• 1999

압력을 증가시켜가며 맥파를 측정하여 맥파의 진동수와 푸리에 진폭이 가해준 압력에 따라 어떠한 양상을 보이는지 조사하였다. 맥파의 기본 진동수는 압력에 따른 변화를 거의 보이지 않았으며, 푸리에 진폭은 개인의 체질에 따라 몇 가지 유형으로 분류될 수 있음을 보였다. 이 유형들을 다시 푸리에 진폭이 최고점에 이를 때의 압력의 크기와 최고점에서의 상태를 유지할 수 있는 압력의 범위에 따라 맥상의 여러 형태와 연관지을 수 있음을 보였다.

• 전자공학회논문지C
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• 제35C권3호
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• pp.97-107
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• 1998

In face recognition based on the Karhunen-Loeve approximation, amplitudespectra of Fourier transformed facial images were used. We found taht the use of amplitude spetra gives not only the shift-invariance property but also some improvment of recognition rate. This is because the distance between the varing faces of a person compared with that between the different persons perfomed computer experiments on face recognitio with varing facial images obtained from total 55 male and 25 females. We confirmed that the use of amplitude spectra of Fourier-trnsformed facial imagesgives better recognition rate for avariety of varying facial images including shifted ones than the use of direct facial images does.

• 지구물리
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• 제6권1호
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• pp.25-29
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• 2003

3성분 지진기록을 주파수 영역에서 벡터적으로 합성하여 퓨리에 진폭스펙트럼 분석의 불확실성을 저감하는 방법을 제시하였다. 3성분 합성 퓨리에 진폭스펙트럼을 이용한 분석기법은 두 가지 장점이 있다. 첫째, 단일 성분에서 나타나는 벡터 분할비를 제거함으로써 지진모멘트 추정의 신뢰도를 향상시킨다. 둘째, 퓨리에 스펙트럼의 형상을 강화시킴으로써 지진모멘트, 모서리 주파수, 고주파성분 감쇠상수($χ$) 등을 정확하게 추정할 수 있다. 특히, 두 번째 장점은 신호/잡음비가 낮은 미소지진 기록의 분석에 유용하다.

• 한국유변학회:학술대회논문집
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• 한국유변학회 2000년도 춘계 학술발표회 논문집
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• pp.62-65
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• 2000

• 전자공학회논문지C
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• 제35C권8호
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• pp.60-67
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• 1998

We studied the effects of fractional fourier transform in face recognition, in which only the amplitude spectra of transformed facial images were used.We used two recently developed face recognition methods, the most effective feature (MEF) method (i.e., eigenface method) and most discriminating feature (MDF) method, and the effects of th etransform for th etwo methods were consistent. We confirmed that the recognition rate by the use of MDF method is better than that consistent. We confirmed that the recognition rate by the use of MDF method is better than that by MEF regardless of the order to transform, these methods provided slightly better results when the order was 1 than for any other order values. Only when the order was close to 1, the recognition rates were robust to the shift of the input images, and the trend that the recognition rates decreased as the input size varied was independent of the order. From these results, we fond that it is most advantageous to use the amplitude spectra of the conventional fourier transform whose order is 1.

• 한국정밀공학회지
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• 제20권5호
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• pp.171-179
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• 2003

An Amplitude Proportional Friction Damper (APFD) is considered in order to improve the characteristics of Coulomb friction damper. The frictional force is proportional to the amplitude in APFD system and the system is non-linear as is Coulomb damper system. A free vibration analysis on the 1-DOF system has made to demonstrate the characteristics of the APFD system. The results show that APFD system has similar damping characteristics to the viscous damper. Also, the solution for the response of a base-excited system with APFD is developed through the application of a Fourier series to represent the frictional force of APFD. It is assumed that no stick-slips occur during any portion of the steady-state oscillation.

• Earthquakes and Structures
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• 제20권4호
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• pp.457-471
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• 2021

This study aims at providing a simple and effective methodology to define a meaningful characteristic period for special class of earthquake records named "pulse-like ground motions". In the proposed method, continuous wavelet transform is employed to extract the large pulse of ground motions. Then, Fourier amplitude spectra obtained from the original ground motion and the residual motion is simply compared. This comparison permits to define a threshold pulse-period (Tp∗) as the threshold period above which the pulse component has negligible contributions to the Fourier amplitude spectrum. The effect of pulse on frequency content of motions was discussed on the light of this definition. The advantage and superior features of the new definition were related to the inelastic displacement ratio (IDR) for single-degree-of-freedom systems with period equal to one half of the threshold period. Analyses performed for the proposed period at three ductility levels u=2,4,6 were compared with the results obtained at half of pulse period derived from wavelet analysis, peak-point method and the peak of product of the velocity and the displacement response spectra (Sv x Sd). According to the results, pulse effects on inelastic displacement ratio seem to be more important when $\frac{T_p^*}{T}=2$ (T is the fundamental vibration period of system). The results showed that utilizing of the proposed definition could facilitate an enhanced understanding of pulse-like records features.

• Korea-Australia Rheology Journal
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• 제18권2호
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• pp.91-98
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• 2006

We compare FT (Fourier Transform) and SD (Stress Decomposition), the interpretation methods for LAOS (Large Amplitude Oscillatory Shear). Although the two methods are equivalent in mathematics. they are significantly different in numerical procedures. Precision of FT greatly depends on sampling rate and length of data because FT of experimental data is the discrete version of Fourier integral theorem. FT inevitably involves unnecessary frequencies which must not appear in LAOS. On the other hand, SD is free from the problems from which FT suffers, because SD involves only odd harmonics of primary frequency. SD is based on two axioms on shear stress: [1] shear stress is a sufficiently smooth function of strain and its time derivatives; [2] shear stress satisfies macroscopic time-reversal symmetry. In this paper, we compared numerical aspects of the two interpretation methods for LAOS.

• Journal of the Optical Society of Korea
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• 제19권2호
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• pp.149-153
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• 2015

A digital micro-mirror device (DMD) has the potential to modulate an incident wave with high speed, and the application for holographic display has been studied by many researchers. However, the quality of reconstructed image isn't good in comparison with that from a gray-scale amplitude-only hologram since it is a binary amplitude-only spatial light modulator (SLM). In this paper, we suggest a method generating a set of binary holograms to improve the quality of the reconstructed image. Here, we are concerned with the case for which the object plane is positioned at the Fourier domain of the plane of the SLM. In this case, any point in the Fourier plane is related to all points in the hologram. So there is a chance to generate a set of binary holograms illuminated by incident wave with constant optical power. Moreover, we find an interesting fact that the quality of reconstructed image is improved when the spatial frequency bandwidth of the binary hologram is limited. Therefore, we propose an iterative segmentation algorithm generating a set of binary holograms that are designed to be illuminated by the wave with constant optical power. The feasibility of our method is experimentally confirmed with a DMD.