• 대한임베디드공학회논문지
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• 제6권3호
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• pp.168-173
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• 2011

In this paper, an optical image hiding technique using real-valued decoding key is proposed. In the embedding process, a each zero-padded original image placed in a quadrants on an input plane is multiplied by a statistically independent random phase pattern and is Fourier transformed. An encoded image is obtained by taking the real-valued data from the Fourier transformed image. And then a phase-encoded pattern, used as a hidden image and a decoding key, is generated by the use of multiple phase wrapping from the encoded images. A transmitted image is made from the linear superposition of the weighted hidden images and a cover image. In reconstruction process, the mirror reconstructed images can be obtained at two quadrants by the inverse-Fourier transform of the product of the transmitted image and the decoding key. Computer simulation and optical experiment are demonstrated in order to confirm the proposed technique.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2009년도 학술대회
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• pp.436-442
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• 2009

삼차원 재구성 기법은 대상을 파괴하지 않고도 그 내부 구조의 공간적 해석을 가능하게 해주는 단층 영상을 생성해주기 때문에, 산업, 의료분야에서 널리 사용되고 있다. 최근 영상 장비의 성능 향상으로 고해상도의 CT 영상을 얻을 수 있게 되었으나, 대용량 데이터를 재구성하기 위해 많은 시간이 소요된다. 본 논문에서는 재구성에서 가장 많은 시간이 소요되는 여과와 역투사 과정을 범용 그래픽스 하드웨어를 사용하여 최적화하는 방법을 제안한다. 여과에서는 네 장의 영상을 압축하여 동시에 처리하는 기법을 적용하고, 역투사 과정에서는 깊이 테스트를 이용하여 계산량을 줄이는 방법을 사용한다. 제안된 방법으로 구현된 GPU 기반 프로그램은 OpenMP 를 사용하여 최적화 된 CPU 기반 프로그램에 비해 약 50 배 이상 속도가 향상되었다.

• Applied Microscopy
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• 제38권1호
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• pp.63-72
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• 2008

Allen et al. (2004)에 의해 개발된 IWFR 방법에 대해서 응용성에 관심을 가지고 고찰되었다. 이 고찰에는 문헌에 보고된 GaAs, $YBa_2CuO_7$ 및 $Al_2CuMg$의 재료에 대한 HRTEM 연구물들이 이용되었다. 이 고찰 과정에서 이 방법의 타당성에 대한 이론적 근거, 제한조건 및 정보한계들을 명확히 제시되었다. IWFR 방법을 통해 얻은 결정 밑 표면에 전자 파동함수의 상(phase)-영상은 구면수차에 의한 영상 왜곡이 교정된 정보한계 범위 내에서 원자분해상을 나타낼 뿐만 아니라 결정의 구성원자의 원자번호에 대체적으로 비례하는 강도 분포를 나타내는 강한 경향이 있음이 특히 주목되었다.

• 천문학회보
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• 제41권1호
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• pp.46.1-46.1
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• 2016

The formation process of a current sheet is important for solar flare from a viewpoint of a space weather prediction. We therefore derive the temporal development of the spatial and statistical distribution of electric current density distributed in a flare-producing active region to describe the formation of a current sheet. We derive time sequence distribution of electric current density by applying a nonlinear force-free approximation reconstruction to Active Region 12158 that produces an X1.6-class flare. The time sequence maps of photospheric vector magnetic field used for reconstruction are captured by a Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamic Observatory (SDO) on 10th September, 2014. The spatial distribution of electric current density in NLFFF model well reproduce observed sigmoidal structure at the preflare phase, although a layer of high current density shrinks at the postflare phase. A double power-law profile of electric current density is found in statistical analysis. This may be expected to use an indicator of the occurrence of a solar flare.

• 인터넷정보학회논문지
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• 제10권2호
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• pp.179-186
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• 2009

본 논문은 가중 퍼지소속함수 기반 신경망(Neural Network with Weighted Fuzzy Membership Functions, NEWFM)을 이용하여 Creighton University Ventricular Tachyarrhythmia DataBase(CUDB)의 심전도(ECG) 신호로부터 정상리듬(Normal Sinus Rhythm, NSR)과 심실빈맥/심실세동(Ventricular Tachycardia/Ventricular Fibrillation, VT/VF)을 분류하는 방안을 제시하고 있다. NEWFM에서 사용할 특징입력을 추출하기 위해서 첫 번째 단계에서는 웨이블릿 변환(wavelet transform, WT)을 이용하였다. 두 번째 단계에서는 첫 번째 단계에서 생성된 웨이블릿 계수들을 위상공간 재구성(Phase Space Reconstruction, PSR)과 첨단(Peak) 추출 기법의 입력 값으로 이용하여 2개의 특징입력을 추출하였다. NEWFM은 이들 2개의 특징입력을 이용하여 정상리듬과 심실빈맥/심실세동을 분류하였고 그 결과로 90.13%의 분류성능을 나타내었다.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.2968-2976
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• 2021

This paper introduces a method to reconstruct the three-dimensional (3D) microstructure of two-phase materials, e.g., porous materials such as highly irradiated nuclear fuel, from two-dimensional (2D) sections via a multi-objective optimization genetic algorithm. The optimization is based on the comparison between the reference and reconstructed 2D sections on specific target properties, i.e., 2D pore number, and mean value and standard deviation of the pore-size distribution. This represents a multi-objective fitness function subject to weaker hypotheses compared to state-of-the-art methods based on n-points correlations, allowing for a broader range of application. The effectiveness of the proposed method is demonstrated on synthetic data and compared with state-of-the-art methods adopting a fitness based on 2D correlations. The method here developed can be used as a cost-effective tool to reconstruct the pore structure in highly irradiated materials using 2D experimental data.

• Journal of Power Electronics
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• 제13권5호
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• pp.884-895
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• 2013

In this paper, the Fourier-based PLL (Phase-locked Loop) is introduced with a new structure, capable of selective harmonic detection in single and three-phase systems. The application of the FB-PLL to harmonic detection is discussed and a new model applicable to three-phase systems is introduced. An analysis of the convergence of the FB-PLL based on a linear model is presented. Simulation and experimental results are included for performance analysis and to support the theoretical development. The decomposition of an input signal in its harmonic components using the Fourier theory is based on previous knowledge of the signal fundamental frequency, which cannot be easily implemented with input signals with varying frequencies or subjected to phase-angle jumps. In this scenario, the main contribution of this paper is the association of a phase-locked loop system, with a harmonic decomposition and reconstruction method, based on the well-established Fourier theory, to allow for the tracking of the fundamental component and desired harmonics from distorted input signals with a varying frequency, amplitude and phase-angle. The application of the proposed technique in three-phase systems is supported by results obtained under unbalanced and voltage sag conditions.

• 한국광학회지
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• 제21권4호
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• pp.146-150
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• 2010

디지털 홀로그래피에서 재생상을 재생할때 복소공액 홀로그램을 도입하여 위상 왜곡과 잡음이 제거된 재생 영상을 얻는 방법에 대하여 연구하였다. 일반적으로 디지털 홀로그램은 시료의 위상 정보 외에 위상 정보에 겹쳐져 있어 잡음으로 작용하는 허상, DC항 뿐만 아니라 측정 시스템의 위상 왜곡 현상도 모두 포함되어 기록된다. 기록된 홀로그램에서 시료의 위상 정보만을 분리하여 이를 재생하면 질 좋은 위상 재생상을 얻을 수 있다. 본 연구에서는 복소공액 홀로그램을 이용하면 off-axis 및 in-line 홀로그래피에서 위상왜곡과 측정시스템이 가지고 있는 잡음을 제거 할 수 있음을 실험적으로 확인하였다.

• Current Optics and Photonics
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• 제2권6호
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• pp.540-546
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• 2018

We propose an implementation scheme for an optical encryption system with hybrid-pattern random keys. In the encryption process, a pair of random phase keys composed of a white-noise phase key and a structured phase key are positioned in the input plane and Fourier-spectrum plane respectively. The output image is recoverable by digital reconstruction, using the conjugate of the encryption key in the Fourier-spectrum plane. We discuss the system encryption performance when different combinations of phase-key pairs are used. To measure the effectiveness of the proposed method, we calculate the statistical indicators between original and encrypted images. The results are compared to those generated from a classical double random phase encoding. Computer simulations are presented to show the validity of the method.

• 건축역사연구
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• 제24권4호
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• pp.7-18
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• 2015

Gwanghwamun was dismantled and displaced to the east side of the palace, at that time, the Chosun Government General Building was constructed in the Gyeongbokgung palace. After the Korea war, it remained as a stonework as a result of the fire. In 1968, The Gwanghwamun came back in front of the palace. Then, why it was rebuilt in the 3rd Republic period? What was the reason for selecting concrete? Since the May 16 coup, the military regime had been utilized palace and surrounding urban space to show a visible practice of modernization. Attempting the combination of modern technology in the 1960s and traditional cultural property and reconstructing a city as a pretext called Cultural Heritage conservation was a typical mechanism of the 1960s. In this study, I start by assume that reconstructing Gwanghwamun(1968) was a part of project to change the surrounding urban space of Gwanghwamun than to preserve cultural assets. Two main contributions of the study are following. First, I collect availabe data on the reconstructing surrounding urban space of the Gwanghwamun and re-organize them in chronological order to make them as fragments of a map. Second, I analysis and identify the nature and phase of the Gwanghwamun reconstruction.