• 한국연소학회지
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• 제12권1호
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• pp.1-10
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• 2007

Analytical investigation of acoustic wave scattering from turbulent premixed flames was conducted to evaluate the acoustic energy amplification/damping. Such acoustic energy change is attributed to the acoustic velocity jump due to flame's heat release. Small perturbation method up to second order and stochastic analysis were utilized to formulate net acoustic energy and the energy transfer from coherent to incoherent energy. Randomly wrinkled flame surface is responsible for the energy transfer from coherent to incoherent field. Nondimensional parameters that govern net acoustic energy were determined: rms height and correlation length of flame front, incident wave frequency, incidence angle, and temperature ratio. The dependence of net acoustic energy upon these parameters is illustrated by numerical simulations in case of Gaussian statistics of flame front. Total net energy was amplified and the major factors that affect such energy amplification are incidence angle and temperature ratio. Coherent (incoherent) energy is damped (amplified) with rms height and correlation length of flame front.

• 조명전기설비학회논문지
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• 제27권11호
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• pp.1-6
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• 2013

It is introduced the phase error sources of a incoherent hologram in incoherent triangular holography and derived the reconstruction image of point-source including the phase error in the lateral direction. From the reconstruction image of point-source, we analyzed the effect of phase error on the lateral resolution. When the phase retardation errors and azimuth angle error of a wave plate and a polarizer range from 0 to $2{\pi}/15$, the normalized intensities of reconstructed images are down by about 0.1% and 2.3%, respectively.

• 소음진동
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• 제6권6호
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• pp.835-842
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• 1996

To identify the locations and strengths of acoustic sources, one may use a microphone line array. Apparent advantage of the source identification method utilizing a line array is that it requires less measurement points than intensity method and holography. This method is based on the information of magnitude and phase difference between pressure signals at each microphone. Since those differences are dependent on the source model, we have to assume them such as plane, monopole, etc. In this paper the conventional source identification methods such as beamforming method and MUSIC method are briefly reviewed by modeling a source as plane and spherical wave, then a modified method is introduced. This can be applied to sound field which may by either coherent or incoherent. Typical simulations and experiment are performed to confirm this identification method.

• 소음진동
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• 제9권5호
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• pp.922-927
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• 1999

The objective of this paper is to obtain the contribution of each source to the spectrum of pressure, when there are multiple incoherent sources in near-field acoustic holography. For this objective, we have to obtain signals very coherent to the input signals of the sources. To obtain the very coherent signals, many people have measured pressure signals in the vincinity of the sources. However, it is sometimes difficult to locate microphones near to the sources so that the signals are very coherent to the input signals. This paper proposed a method to obtain the very coherent signals by near-field acoustic holography. Therefore, the proposed method does not require the measurement of pressure near to each source. Simulation results for two incoherent monopole sources showed the possibility of the proposed method.

• 한국광학회지
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• 제10권2호
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• pp.128-137
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• 1999

변형 삼각간섭계에 있어서 기록과 복원 시스템을 고려한 PSF를 구하였다. 그리고 변형 삼각간섭계와 Cochran 삼각간섭계의 해상도를 유도하였으며, 렌즈의 배율, 복원시에 사용되는 레이저의 파장, 그리고 홀로그램의 크기에 따른 두 시스템의 해상도를 구하고 분석하였다. 또한, 인코히어런트 홀로그래피의 가능성을 입증하기 위하여 수은등을 이용한 인코히어런트 홀로그램의 생성과 이를 이용한 광학적 복원 결과가 제시되었다.

• Bulletin of the Korean Chemical Society
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• 제28권4호
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• pp.607-612
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• 2007

Relationship between charge transfer mechanism and quantum coherence has been investigated using a realtime quantum dynamics approach. In the on-the-fly filtered propagator functional path integral simulation, by separating paths that belong to different mechanisms and by integrating contributions of correspondingly sorted paths, it was possible to accurately obtain quantitative contribution of different transport mechanisms. For a 5'-GAGGG-3' DNA sequence, we analyze charge transfer processes quantitatively such that the governing mechanism alters from coherent to incoherent charge transfer with respect to the friction strength arising from dissipative environments. Although the short DNA sequence requires substantially strong dissipation for completely incoherent hopping transfer mechanism, even a weak system-environment interaction markedly destroys the coherence within the quantum mechanical system and the charge transfer dynamics becomes incoherent to some degree. Based on the forward-backward path deviation analysis, the coherence variation depending on the environment is investigated numerically.

• 한국광학회지
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• 제24권2호
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• pp.92-98
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• 2013

회전검광자 방식의 타원계 구조에 기초하여 두꺼운 막들 내부에서 일어나는 다중반사에 인한 빛의 세기를 결맞지 않도록 중첩함으로써 결맞음길이보다 두꺼운 막 두 개가 다층박막시료 위에 있을 때 적용되는 타원상수 표현들을 유도하였다. 유도된 표현들을 커버유리와 공기층 아래에 있는 산화규소 박막이 코팅되어 있는 시료의 타원법 분석에 적용하여 그 유용성을 확인하였다.

• 대한전자공학회논문지
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• 제23권6호
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• pp.961-967
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• 1986

A technique of optical image synthesis with an extended incoherent source is presented and compared with the coherent method. A holographic diffraction grating is fabricated by using Michelson interferometer, and by equalizing the 8th-order to the 2nd-order diffraction efficiency, complex amplitude addition and subtracdtion of optical images are simultaneously realized. The experiment shows that the quality of synthesized optical images in the incoherent method is improved in comparison with that of the coherent method by suppressing the coherent artifact noise.

• Journal of the Optical Society of Korea
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• 제16권3호
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• pp.256-262
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• 2012

We derive the point-spread function of the reconstructed image from a point-source complex hologram, which includes phase error caused by polarization components, in the longitudinal direction of the point-spread function and analyze the effect of the error sources of polarization components having influence on image reconstruction of a point-source complex hologram in incoherent triangular holography.

• 한국항행학회논문지
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• 제16권2호
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• pp.240-246
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• 2012

지금까지의 힐버트 변환은 대부분 코히어런트 이미징에서만 활용되어 왔을 뿐 인코히어런트 이미징에 대해서는 그 적용이 미비했다. 본래의 광원 영역에서는 인코히어런트 물체의 힐버트 변환이 일정하게 중첩되는 문제가 발생하기 때문이다. 본 논문에서는 음이 아닌 강도(intensity) 분포 함수의 합성을 수행함으로써 인코히러언트 이미징의 문제점을 보완한 two-pupil 시스템을 적극 활용하여 코히어런트 이미징 대비 낮은 노이즈 특성, 물체의 위상 변화에 대한 강건함, 유연한 필터의 설계 등의 장점을 극대화한다. 제안하는 이미징 방식은 공간영역에서 광학 전달 함수를 분할하여 필터링한 후 인코히어런트 물체의 힐버트 변환을 수행한다. 이를 바탕으로 광학 시스템에서의 두 pupil을 수학적으로 분석하고 디자인하여 two-pupil 광학 헤테로다인 스캐닝 시스템을 구현할 수 있다. 모의실험을 통해 제안하는 시스템을 바탕으로 2-D 홀로그램을 도출함으로써 인코히어런트 이미징에서도 힐버트 변환의 적용이 유효함을 확인할 수 있다. 또한 복소홀로그램의 복원을 통해 힐버트 변환만을 이용한 홀로그램에 비해 공간 영역에서 선명도가 개선된 홀로그램 영상도 획득할 수 있다.