• Title, Summary, Keyword: Phase encoding

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An Efficient Multicasting Algorithm and Its Performance Evaluation in Multistage Interconnection Networks (다단계 상호연결망에서 효율적인 멀티캐스팅 알고리즘과 성능 평가)

  • Kim, Jin-Soo;Chang, Jung-Hwan
    • The Journal of the Korea Contents Association
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    • v.6 no.2
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    • pp.84-92
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    • 2006
  • In this paper, we propose an efficient multicasting algorithm in multistage interconnection networks (MIN's) employing the region encoding scheme. The proposed algorithm uses the recursive scheme to recycle a multicast message at most two times through MIN, in order to send it to its desired destinations. It is composed of two recycling phases which are the copying phase and the routing phase of the multicast message. In the first phase, a source sends the message to a region that contains the largest number of destination regions, and destinations in these regions receive and store the message in this phase. The remaining destinations can finally receive the message in the second phase. This method of the algorithm can improve its performance by reducing the delay of message and the volume of traffic. Moreover, we evaluate the performance of our algorithm in terms of the average number of recycling and the number of internal links used per destination, comparing with the previously proposed algorithm.

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A NMF-Based Speech Enhancement Method Using a Prior Time Varying Information and Gain Function (시간 변화에 따른 사전 정보와 이득 함수를 적용한 NMF 기반 음성 향상 기법)

  • Kwon, Kisoo;Jin, Yu Gwang;Bae, Soo Hyun;Kim, Nam Soo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38C no.6
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    • pp.503-511
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    • 2013
  • This paper presents a speech enhancement method using non-negative matrix factorization. In training phase, we can obtain each basis matrix from speech and specific noise database. After training phase, the noisy signal is separated from the speech and noise estimate using basis matrix in enhancement phase. In order to improve the performance, we model the change of encoding matrix from training phase to enhancement phase using independent Gaussian distribution models, and then use the constraint of the objective function almost same as that of the above Gaussian models. Also, we perform a smoothing operation to the encoding matrix by taking into account previous value. Last, we apply the Log-Spectral Amplitude type algorithm as gain function.

Encrypted holographic storage using double-phase encoding technique

  • Vu, Tien-Viet;Kim, Nam;Jeon, Seok-Hui
    • Proceedings of the Optical Society of Korea Conference
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    • pp.229-230
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    • 2007
  • Several encryption techniques were successfully applied to secure holographic memory systems.[1,2] In these systems the reference beam, object beam, or both can be encoded optically. Optics provides many degrees of freedom with which the optical beam may be encoded, such as amplitude, phase, wavelength, and polarization.

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Image Security and Personal Identification using CGH and Phase Mask (CGH와 위상 마스크를 이용한 영상 보안 및 개인 인증)

  • 김종윤;박세준;김종찬;김철수;조웅호;김수중
    • Proceedings of the IEEK Conference
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    • pp.958-961
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    • 1999
  • A new image encoding and identification scheme is proposed for security verification by using CGH(computer generated hologram), random phase mask, and correlation technique. The encrypted image, which is attached to the security product, is made by multiplying QPH(quadratic phase hologram) using SA(simulated annealing) algorithm with a random phase function. The random phase function plays a role of key when the encrypted image is decrypted. The encrypted image could be optically recovered by 2-f system and automatically verified for personal identification. Simulation results show the proposed method cand be used for the reconstruction and the recognition of the encrypted. Image.

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Parabolic mirror test using Computer Generated Hologram (Computer Generated Hologram을 이용한 포물명경 형상측정)

  • 김성하;곽종훈;최옥신;송재봉;이윤우;이인원
    • Korean Journal of Optics and Photonics
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    • v.11 no.2
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    • pp.80-84
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    • 2000
  • Parabolic almninium mlITOr of m.5('||'&'||'cent; 50 nun) was fabncated by a diamond tummg machine. Computer generated hologram (CGH) for the test of parabolic mirror was encoded by binary phase hologram Approximation of curved fringe to line was made by staircase encoding. After fringe data 1ransformed mto a Post Scnpt file. magnified master CGH was printed by a laser printer, and then it reduced to the photographIc film. Parabolic mirror was tested by Twyman-Green interferometer with CGH at VIewing arm. Its experimental result was compared with those of surface profile and auto-collimatIon test, and then the errors were analyzed.

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Optimized Encoding of Sudoku Puzzle for SAT Solvers (SAT 처리기를 위한 수도쿠 퍼즐의 최적화된 인코딩)

  • Kwon, Gi-Hwon
    • Journal of KIISE:Software and Applications
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    • v.34 no.7
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    • pp.616-624
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    • 2007
  • Sudoku can be regarded as a SAT problem. Various encodings are known for encoding Sudoku as a Conjunctive Normal Form (CNF) formula, which is the standard input for most SAT solvers. Using these encodings for large Sudoku, however, generates too many clauses, which impede the performance of state-of-the-art SAT solvers. This paper presents an optimized CNF encodings of Sudoku to deal with large instances of the puzzle. We use fixed cells in Sudoku to remove redundant clauses during the encoding phase. This results in reducing the number of clauses and a significant speedup in the SAT solving time.

${T_2}weighted$- Half courier Echo Planar Imaging

  • 김치영;김휴정;안창범
    • Investigative Magnetic Resonance Imaging
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    • v.5 no.1
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    • pp.57-65
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    • 2001
  • Purpose : $T_2$-weighted half courier Echo Planar Imaging (T2HEPI) method is proposed to reduce measurement time of existing EPI by a factor of 2. In addition, high $T_2$ contrast is obtained for clinical applications. High resolution single-shot EPI images with $T_2$ contrast are obtained with $128{\times}128$ matrix size by the proposed method. Materials and methods : In order to reduce measurement time in EPI, half courier space is measured, and rest of half courier data is obtained by conjugate symmetric filling. Thus high resolution single shot EPI image with $128{\times}128$ matrix size is obtained with 64 echoes. By the arrangement of phase encoding gradients, high $T_2$ weighted images are obtained. The acquired data in k-space are shifted if there exists residual gradient field due to eddy current along phase encoding gradient, which results in a serious problem in the reconstructed image. The residual field is estimated by the correlation coefficient between the echo signal for dc and the corresponding reference data acquired during the pre-scan. Once the residual gradient field is properly estimated, it can be removed by the adjustment of initial phase encoding gradient field between $70^{\circ}$ and $180^{\circ}$ rf pulses. Results : The suggested T2EPl is implemented in a 1.0 Tela whole body MRI system. Experiments are done with the effective echo times of 72ms and 96ms with single shot acquisitions. High resolution($128{\times}128$) volunteer head images with high $T_2$ contrast are obtained in a single scan by the proposed method. Conclusion : Using the half courier technique, higher resolution EPI images are obtained with matrix size of $128{\times}128$ in a single scan. Furthermore $T_2$ contrast is controlled by the effective echo time. Since the suggested method can be implemented by software alone (pulse sequence and corresponding tuning and reconstruction algorithms) without addition of special hardware, it can be widely used in existing MRI systems.

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QPSK Modulation Based Optical Image Cryptosystem Using Phase-shifting Digital Holography

  • Jeon, Seok-Hee;Gil, Sang-Keun
    • Journal of the Optical Society of Korea
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    • v.14 no.2
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    • pp.97-103
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    • 2010
  • We propose a new technique for the optical encryption of gray-level optical images digitized into 8-bits binary data by ASCII encoding followed by QPSK modulation. We made an encrypted digital hologram with a security key by using 2-step phase-shifting digital holography, and the encrypted digital hologram is recorded on a CCD camera with 256 gray-level quantized intensities. With these encrypted digital holograms, the phase values are reconstructed by the same security key and are decrypted into the original gray-level optical image by demodulation and decoding. Simulation results show that the proposed method can be used for cryptosystems and security systems.