• 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.

• 전자공학회논문지A
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• 제29A권7호
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• pp.64-72
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• 1992

VLSI 전송선로의 커패시턴스를 3차원으로 계산하였다. Green's function과 표면전하밀도의 곱의 형태로 주어지는 적분식을 풀어서 커패시턴스를 구하였다. 이때, 표면전하밀도는 도체의 표면을 균일한 면적을 갖는 미소 면적소로 나누어 주었을 때 각각의 면적소 내에서는 일정한 상수값을 갖는다고 가정하였다. 지금까지의 Green's function을 이용한 적분방법에서는 적분식의 계산을 Fourier 적분의 형태로 변환하여 계산하였기 때문에 계산과정에서 어느정도의 오차가 있을 수 밖에 없었지만, 본 논문에서는 Fourier 적분을 사용하는 대신에 이중 적분을 직접적으로 적분할 수 있는 방법을 제시하였다. 이 방법을 사용하여 적용한 결과를 기존의 결과들과 비교를 함으로써, 이의 정확성을 입증하였다.

• 대한의용생체공학회:의공학회지
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• 제24권6호
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• pp.487-494
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• 2003

수면뇌파의 해석에 있어서 수면단계는 뇌파의 특성파 검출에 특히 중요하다. 수면단계는 여러 수면질환의 진단에 가장 기초적일 단서를 제공한다. 본 연구에서 수면뇌파 신호를 이산 웨이브렛 변환 뿐 만 아니라 퓨우리에 변환, 연속 웨이브렛 변환을 이용해서 해석하였다. 제안된 시스템 방범인 퓨우리에와 웨이브렛은 수면뇌파의 중요한 특성파(유파, 수면방추파, K복합, 구파 REM) 검출을 위해서 수면상태를 분석했다. 수면뇌파 분석에는 Daubechies 웨이브렛 변환 방법과 고속 퓨우리에를 이용했다. 모의실험결과 신경망 시스템이 특성 파형의 분류에 높은 성능을 발휘함을 알 수 있었다.

• Current Optics and Photonics
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• 제6권6호
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• pp.598-607
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• 2022

In this paper, a simple nondestructive technology is used to investigate unstained biological blood cells in three dimensions (3D). The technology employs a reflective phase-only spatial light modulator (SLM) for displaying the phase hologram of the object being tested, and a Fourier lens for its reconstruction. The phase hologram is generated via superposing a digital random phase on the 2D image of the object. The phase hologram is then displayed by the SLM with 256 grayscale levels, and reconstructed by a Fourier lens to present the object in 3D. Since noise is the main problem in this method, the windowed Fourier filtering (WFF) method is applied to suppress the noise of the reconstructed object. The quality of the reconstructed object is refined and the noise level suppressed by approximately 40%. The technique is applied to objects: the National Institute of Standards (NIS) logo, and a film of unstained peripheral blood. Experimental results show that the proposed technique can be used for rapid investigation of unstained biological blood cells in 3D for disease diagnosis. Moreover, it can be used for viewing unstained white blood cells, which is still challenging with an optical microscope, even at large magnification.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.343-346
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• 1998

In this paper a radiation problem for a finite microstrip antenna structure is analyzed. For the analysis of finite structures we utilize the equivalent volume current. Intergral equation for the unknown equivalent volume current induced on a finite microstrip structure is derived and solved by the use of conjugate gradient-fast fourier. transform (CG-FFT) method. Some numerical examples are radiation patterns derived by the equivalent volume current solved by the conjugate gradient-fast fourier transform.

• 응용통계연구
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• 제10권1호
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• pp.137-149
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• 1997

본 논문에서는 푸리에 전개에 기초한 로그밀도추정법을 제안하였다. 삼각함수로 구성된 기저함수들은 베이즈정보 규준량에 근거하여 단계적 추가 및 삭제를 이용하여 결정하였고, 모수의 추정에는 최대가능성 방법을 이용하였다. 기존 자료의 분석 및 모의실험을 통하여 제안된 방법의 성능을 예시하였다.

• 한국자기공명학회논문지
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• 제3권1호
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• pp.36-43
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• 1999

We present a pulse shape tailored for broadband decoupling for a system of spin-1/2's with scalar couplings as well. In crafting the pulse shape Coherent Averaging Theory and Fourier expansion method are used. The Fourier expansion coefficients are optimized numerically by applying the Simulated Annealing Method. The decoupling performance of the shaped pulse thus designed is then compared with the well-known composite pulse sequence, DIPSI-2. It is shown that the shaped pulse performs well even at the conditions where the DIPSI sequence begins to fail.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
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• pp.939-942
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• 1989

Most of systems are included nonlinear characteristics in practice. One might be faced with difficulties when problems of nonlinear systems are solved. In this paper we present a formal linearization method of nonlinear systems by using the trigonometric Fourier expansion on the state space considering easy inversion. An error bound, an application, and a compensation of this method are also investigated.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 추계학술대회논문집
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• pp.138-141
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• 1997

CFM(Cast Forge Method) is widely used in manufacturing industry to produce aluminium parts with good mechanical properties and low production cost. CFM is the process which produces a final products by forging from the initial billet by casting. The study on this paper covers the automatic design method which finds a pertinent shape for initial billet using Fast Fourier Transform, low-pass frequency filtering and FEM simulation of the nonisothermal forging process by DEFORM. These works will give us an information to enhance the low strength of a aluminium casting.

• 대한수학회지
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• 제37권6호
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• pp.1043-1057
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• 2000

This paper is devoted to the investigation of mixed Fourier-Bessel transformation (※Equations, See Full-text) We apply the method of [6] which provides the estimate for weighted L(sub)$\infty$-norm of the spherical mean of │f│$^2$ via its weighted L$_1$-norm (generally it is wrong without the requirement of the non-negativity of f). We prove that in the case of Fourier-Bessel transformatin the mentioned method provides (in dependence on the relation between the dimension of the space of non-special variables n and the length of multiindex ν) similar estimates for weighted spherical means of │f│$^2$, the allowed powers of weights are also defined by multiindex ν. Further those estimates are applied to partial differential equations with singular Bessel operators with respect to y$_1$, …, y(sub)m and we obtain the corresponding estimates for solutions of the mentioned equations.