• Journal of Energy Engineering
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• v.27 no.4
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• pp.13-19
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• 2018

In this study, the lightweight design of butterfly valve disc component for power plant based on topology optimization was performed. Here, commercial finite element (FE) analysis software was used. The external shape of the basic disc model was not deformed, and the internal element density was removed to make it lightweight. Optimal design was performed each other after the disc plate and two brackets attached on the surface of the disc were separated. Once the optimal shapes were selected, they were assembled to build up the 3-D lightweight valve disc model. After applying pressure to this model, FE analysis was performed to confirm the structural safety.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.2
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• pp.343-348
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• 2020

During 50 years, the chaotic theory has begun to research with concerning in Mathematics and physics, and it has extended the fields to of engineering and social science. Recently, chaotic theory has progressed as a type of fusion research fused with natural science and social science. Such fused research includes problems for addiction, happiness of human, problem happened between family and love affairs between man and woman. In this paper, we consider the external environment based on love model which is one among fusion research, and when we consider colored noise in the external environment, we verify how the chaotic pattern is affected in the love model through time series and phase portrait.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2005.11a
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• pp.155-158
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• 2005

MRI 스캔시 화상평면내에서 촬상대상물체의 회전은 MRI 신호에 위상오차와 불균일 표본화를 일으킨다. MRI 신호의 위상오차와 불균일 표본화에 대한 문제의 모델은 화상평면내 임의 중심과 원점에 관한 회전운동에 의해 열화된 MRI 신호들사이에 위상차가 존재함을 나타낸다. 이에 아티팩트가 포함된 MR 화상의 화질을 개선하기위해서 다음과 같은 방법을 제안한다. 우선, 2차원 회전운동의 회전각은 이미 알려져 있고, 회전중심의 위치가 미지인 경우에 대해 위상보정에 기초한 아티팩트를 보정하는 알고리즘과, 다음으로, 회전중심과 각도가 모두 미지인 2차원 회전운동에 대해 아티팩트를 보정하는 알고리즘을 제안한다. 이때, 미지 운동 파라메타를 예측하기위해 촬상대상물체의 경계바깥쪽에서 이상적인 MR 화상의 에너지는 최소가 되고, 촬상대상물체의 회전이 존재할 때 측정된 에너지는 증가한다는 성질을 이용한다. 이러한 성질을 이용해서 각 위상부호화 단계에서 미지의 회전각 크기를 추정하기위한 평가함수가 도입된다. 최종적으로 시뮬레이션 화상 및 실제화상에 적용해서 제안한 본 방법의 유효성을 확인한다.

• Korean Journal of Optics and Photonics
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• v.26 no.3
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• pp.147-154
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• 2015

We propose a method for simultaneously measuring the front and back surface profiles of transparent optical components. The proposed method combines dual-wavelength transmission deflectometry with liquids to record distorted phases at different wavelengths, and then numerically reconstructs the three-dimensional phase information to image the front and back surfaces of the lens. We propose a theoretical model to determine the surface information, and a bifocal lens is experimentally investigated. Unlike conventional transmission deflectometry, our proposed method supports direct observation of the front and back surface profiles of the optical elements.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.7
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• pp.573-581
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• 2014

We proposed a hopping phase estimator to demodulate the received signals without any hopping information in frequency hopping spread spectrum systems. The demodulation process in this paper is as follows: hopped frequency tracking is accomplished by choosing a frequency component with maximum amplitude after taking discrete Fourier transform and a hopping frequency estimator which estimates the phase generated by hopped frequency is established through difference product and down-sampling. We obtained the probability density function and variance performance of the proposed estimator and confirmed that the analysis and the simulation results were agreed with each other.

• The Journal of the Korea Contents Association
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• v.2 no.1
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• pp.32-38
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• 2002

In the AV system, stereophonic system has been studied to produce a realistic sound effect. The width of stereo AV system speakers is narrow, to have the spatial impression of sound effect, widening the sound image is necessary. The direction of sound image depends on the phase delay and the sound pressure level difference between two channels. In this paper, we analyze the relationship between the phase delay and the direction of the sound image relating to the frequency of sound source. Also we experimented to directionally localize the sound image of the pure tone with shifting phases and controling sound pressure love between two channels when the sound is reproduced by two speakers to make a spatial impression of sound effect.

• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.13-17
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• 2017

This paper presents an approach to enable a typical GPS receiver to be much less susceptible to intentional disruption such as jamming and change in link environment. In order for the GPS receiver to cope with jamming and to get adaptivity, a $4{\times}4$ beamforming antenna is designed using metamaterials. The design results show the antenna gain much higher than 5 dBi and the movable beam.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.464-473
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• 1993

The dynamics of phase grating formation with visible light in an optical fiber is investigated. Adopting a simple two-photon local bleaching model, it is shown that the grating self-organize into an ideal grating, where the writing frequency is always in the center of the local band gap, as it evolves. The evolution at each point in the fiber is described in terms of a universal parameter that reduces the coupled partial differential equations describing the system to ordinary differential equatior~s. These equations are used to prove that there exists a fixed point of the grating growth process that corresponds to a perfectly phase-mached grating.

• KIPS Transactions on Software and Data Engineering
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• v.3 no.5
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• pp.195-200
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• 2014

Typical methods of active contour model for object contour extraction are snake and level. Snake is usually faster than level set, but has limitation to compute topology of objects. Level set on the other hand is slower but good at it. In this paper, a new object contour extraction algorithm to use advantage of each is proposed. The algorithm is composed of two main steps. In the first step, snake is used to extract the rough contour and then in the second step, level set is applied to extract the complex contour exactly. 5 binary images and 2 natural images with different contours are simulated by a proposed algorithm. It is shown that speed is reduced and contour is better extracted.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.11
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• pp.1272-1280
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• 2008

In this paper, we have proposed a phase noise model of fast frequency hopping synthesizer with DDS Driven PLL architecture. To accurately model the phase noise contribution of noise sources in frequency hopping synthesizer, they were investigated using model of digital divider for PLL, DAC for DDS and Leeson's model for reference oscillator and VCO. Especially it was proposed that the noise component of low pass filter was considered together with the phase noise of VCO. Under assuming linear operation of a phase locked loop, the phase noise transfer functions from noise sources to the output of synthesizer was analyzed by superposition theory. The proposed phase noise prediction model was evaluated and its results were compared with measured data.