• Proceedings of the Korea Multimedia Society Conference
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• 2002.05c
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• pp.10-15
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• 2002

확장된 마크흐름선도(EMFG : Extended Mark Flow Graph)는 시스템의 동시성이나 병렬성을 잘 표현할 수 있는 방향성 그래프이다. 이를 이용하여 시스템을 모델링하면 개념설계가 가능하고, 상세 동작분석이 용이해짐으로 이산제어시스템이나 시퀀스 제어회로등을 설계할 때 사용될 수 있는 도구이다. 기존 EMFG에서는 타이머에 대한 표기 방법이 미비하여 타이머를 많이 사용하는 분야인 시퀀스제어 설계 및 릴레이 회로의 표현에는 많은 어려움이 있다. 본 논문에서는 타이머 릴레이들의 동작에 대하여 생성지연-소멸 트랜지션, 생성-소멸지연 트랜지션과같이 이중바로 표기된 새로운 트랜지션을 도입하였다. 새로운 트랜지션을 이용하면 타이머들의 동작을 분명하게 표현할 뿐만 아니라 EMFG의 표현을 알고리듬할 수 있다. 그러므로 복잡한 시스템을 모델링할 때 제안된 트랜지션을 이용하면 효율적인 모델링을 할 수 있다.

• Investigative Magnetic Resonance Imaging
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• v.10 no.2
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• pp.70-80
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• 2006

Spin echo gradient moment nulling pulse sequences were designed and implemented on a clinical magnetic resonance imaging system. A new technique was introduced for flow compensation that minimized echo time and effectively suppresses unwanted echoes on the slice selection gradient axis in spin echo sequences. A unified gradient shape was used in all orders of flow compensation up to the third order. A dual-purpose gradient was applied for flow compensation and to reduce unwanted artifacts. The sequences were used to generate images of phantoms and/or human brains. This technique was especially good at reducing eddy currents and artifacts related to imperfection of the refocusing pulse. The developed sequences were found to have shorter echo times and better flow compensation in through-plane flow than those of the previous models that were used by other investigators.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.6
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• pp.471-476
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• 2016

In this paper, recognition system for continuous human action is explained by using motion history image and histogram of oriented gradient with spotter model based on depth information, and the spotter model which performs action spotting is proposed to improve recognition performance in the recognition system. The steps of this system are composed of pre-processing, human action and spotter modeling and continuous human action recognition. In pre-processing process, Depth-MHI-HOG is used to extract space-time template-based features after image segmentation, and human action and spotter modeling generates sequence by using the extracted feature. Human action models which are appropriate for each of defined action and a proposed spotter model are created by using these generated sequences and the hidden markov model. Continuous human action recognition performs action spotting to segment meaningful action and meaningless action by the spotter model in continuous action sequence, and continuously recognizes human action comparing probability values of model for meaningful action sequence. Experimental results demonstrate that the proposed model efficiently improves recognition performance in continuous action recognition system.

• Investigative Magnetic Resonance Imaging
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• v.11 no.2
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• pp.95-102
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• 2007

Purpose: To acquire high-resolution spiral-scan images at higher magnetic field, high homogeneous magnetic field is needed. Field inhomogeneity mapping and in-vivo shimming are important for rapid imaging such as spiral-scan imaging. The rapid scanning sequences are very susceptible to inhomogeneity. In this paper, we proposed a higher-order shimming method to obtain homogeneous magnetic field. Materials and Methods: To reduce measurement time for field inhomogeneity mapping, simultaneous axial/ sagittal, and coronal acquisitions are done using multi-slice based Fast Spin echo sequence. Acquired field inhomogeneity map is analyzed using the spherical harmonic functions, and shim currents are obtained by the multiplication of the pseudo-inverse of the field pattern with the inhomogeneity map. Results: Since the field inhomogeneity is increasing in proportion to the magnetic field, higher order shimming to reduce the inhomogeneity becomes more important in high field imaging. The shimming technique in which axial, sagittal, and coronal section inhomogeneity maps are obtained in one scan is developed, and the shimming method based on the analysis of spherical harmonics of the imhomogenity map is applied. The proposed technique is applicable to a localized shimming as well. High resolution spiral-scan imaging was successfully obtained with the proposed higher order shimming. Conclusion: Proposed pulse sequence for rapid measurement of inhomogeneity map and higher order shimming based on the inhomogeneity map work very well at 3 Tesla MRI system. With the proposed higher order shimming and localized higher order shimming techniques, high resolution spiral-scan images are successfully obtained at 3 T MRI system.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.685-688
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• 2001

본 논문은 MPEG 비디오에서 나타나는 여러 예측 형태의 움직임 벡터를 프레임 타입에 관계없이 단일 예측방향만을 갖도록 새롭게 추정하여 비디오 영상물의 분석에 직접적으로 활용하는 방안에 대해 제시하고 있다. 또한 재 추정된 각 프레임에서의 움직임 벡터를 이용한 비디오 시퀀스 내에서의 객체 추출 및 추적 기법 등에 대해서도 함께 제안하였다. 제안된 알고리즘은 영상에 대한 복원과정을 거치지 않고, 압축 비디오 영역으로부터 쉽게 추출될 수 있는 매크로 블록 영역 상에서 수행되었으며, 실험 결과는 제안된 방법의 높은 성능을 잘 나타내어 주고 있다.

• Information and Communications Magazine
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• v.24 no.4
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• pp.83-94
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• 2007

터보 부호는 AWGN 환경에서 비교적 간단한 복호 알고리즘을 가지면서 낮은 신호대 잡음비에서 뛰어난 에러 성능을 보이는 채널부호이다. 터보 부호는 기본적으로 길쌈 부호를 병렬 연접하는 방식으로, 두 개 이상의 구성 부호화기에 같은 시퀀스의 서로 다른 배열을 적용하는 것이다. 본 논고에서는 터보 부호화 및 복호화의 기본 원리에 대하여 설명하고, 이를 여러 형태의 무선 채널에 적용하는 기술에 대하여 언급하고자 한다. 그리고 연구 방향에 대하여 간략히 제시하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.3
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• pp.81-86
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• 2010

Since CORDIC (COordinate Rotation DIgital Computer) is able to carry out the phase operation, such as vector to phase conversion or rotation of vectors, with adders and shifters, it is well suited for the design of the frequency synchronization unit in OFDM receivers. It is not easy, however, to fully utilize the CORDIC in the OFDM demodulator because of the non-linear characteristics of the direction sequence (DS), which is the representation of the phase in CORDIC. In this paper a new representation method is proposed to linearize the direction sequence approximately. The maximum phase error of the linearized binary direction sequence (LBDS) is also discussed. For the purpose of designing the hardware, the architectures for the binary DS (BDS) to LBDS converter and the LBDS to BDS inverse converter are illustrated. Adopting LBDS, the overall frequency synchronization hardware for OFDM receivers can be implemented fully utilizing CORDIC and general arithmetic operators, such as adders and multipliers, for the phase estimation, loop filtering of the frequency offset, derotation for the frequency offset correction. An example of the design of 22 bit LBDS for the T-DMB demodulator is also presented.

• Journal of Korea Multimedia Society
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• v.12 no.7
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• pp.929-940
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• 2009

This paper presents multipurpose watermarking scheme in coutourlet transform domain for copyright protection, authentication and transform detection. Since contourlet transform can detect more multi direction edge and smooth contour than wavelet transform, the proposed scheme embeds multi watermarks in contourlet domain based on 4-level Laplacian pyramid and 2-level directional filter bank. In the first stage of the robust watermarking scheme for copyright protection, we generates the sequence of circle patterns according to watermark bits and projects these patterns into the average of magnitude coefficients of high frequency directional subbands. Then the watermark bit is embedded into variance distribution of the projected magnitude coefficients. In the second stage that is the semi-fragile watermarking scheme for authentication and transform detection, we embed the binary watermark image in the low frequency subband of higher level by using adaptive quantization modulation scheme. From the evaluation experiment using Checkmark 2.1, we verified that the proposed scheme is superior to the conventional scheme in a view of the robustness and the invisibility.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.11a
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• pp.1328-1331
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• 2013

본 논문에서는 스마트폰 내장 가속도 센서를 이용한 2단계 행위 인식 시스템을 제안한다. 제안하는 행위 인식 시스템에서는 행위 별 시간에 따른 가속도 센서 데이터의 변화 패턴을 충분히 반영하기 위해, 1단계 분류에서는 결정트리 모델 학습과 분류를 수행하고, 2단계 분류에서는 1단계 분류 결과들의 시퀀스를 이용하여 HMM모델 학습과 분류를 수행하였다. 또한, 본 논문에서는 특정 사용자나 스마트폰의 특정 위치, 방향 변화에도 견고한 행위 인식을 위하여, 동일한 행위에 대해 사용자와 스마트폰의 위치, 방향을 변경하면서 다양한 훈련 데이터를 수집하였다. 6720개의 가속도 센서 데이터를 이용하여 총 6가지 실내 행위들을 인식하기 위한 실험들을 수행하였고, 그 결과 높은 인식 성능을 확인 할 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4C
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• pp.406-412
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• 2003

A fast multiple object motion detection method using periodogram has been proposed. Each frame is projected to vertical and horizontal directions, and then temporal FFT is applied. A line in two dimensional frequency domain indicates velocity. To estimate the velocity of an object, we intergrate along a line which passes through the origin in frequency domain. If a frame contains multiple moving objects, multiple peaks are detected corresponding to the velocity of each object. After pairing these peaks, we can determine the velocities of an object. In the proposal method we can easily pair horizontal and vertical velocity components efficiently with simple computation by combining projections in 45$^{\circ}$ and 135 $^{\circ}$ directions in addition to the vertical and horizontal direction.