• Proceedings of the IEEK Conference
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• 2000.06d
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• pp.43-46
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• 2000

In this paper, we propose a fast adaptive diamond search algorithm(FADS) for block matching motion estimation. Fast motion estimation algorithms reduce the computational complexity by using the UESA (Unimodal Error Search Assumption) that the matching error monotonically increases as the search moves away from the global minimum error. Recently many fast BMAs(Block Matching Algorithms) make use of the fact that the global minimum points in real world video sequences are centered at the position of zero motion. But these BMAs, especially in large motion, are easily trapped into the local minima and result in poor matching accuracy. So, we propose a new motion estimation algorithm using the spatial correlation among the adjacent blocks. We change the origin of search window according to the spatially adjacent motion vectors and their MAE(Mean Absolute Error). The computer simulation shows that the proposed algorithm has almost the same computational complexity with UCBDS(Unrestricted Center-Biased Diamond Search)〔1〕, but enhance PSNR. Moreover, the proposed algorithm gives almost the same PSNR as that of FS(Full Search), even for the large motion case, with half the computational load.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.331-334
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• 2005

움직임 추정은 비디오신호의 압축에 중요한 역할을 한다. 본 논문은 효율적으로 움직임 벡터를 찾기 위하여 움직임 벡터의 시간적, 공간적 유사성을 이용하였다. 벡터를 검색하기 이전에 움직임 벡터의 검색 범위를 크게 9개의 영역으로 나눈 후, 이전 프레임에서 동일한 위치, 현재 프레임의 현재 매크로블록의 상위, 상우와 좌측의 매크로블록에서의 움직임 벡터까지 총 4개의 움직임 벡터를 이용하여 9개의 영역 중 한 영역을 제 1 후보, 그를 둘러싼 영역을 제 2 후보라 정하고 극소점들(Local Minima)을 피하였다. 모의실험을 통한 결과 NDS(New Diamond Search) 알고리즘에 비하여 매크로블록 당 평균 탐색 포인트 수가 5.79 포인트 감소하고, MSE는 최대 104.23 감소한 것을 확인할 수 있었다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.253-258
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• 1993

In this paper, we propose a new method to extract the line spectrum pair (LSP) frequencies. When speech signal is analyzed by the autocorrelation method, the spectral difference in the logarithmic spectra of the model at steps p and p-1 oscillates. There are p-1 frequency points where the values of the spectral dfference take on either maximum or minimum between 0 and half sampling frequency. We show that these frequencies are excatly the LSP frequencies of order p-1, which can be found by searching the frequencies where the spectral difference reaches either maxima or minima. also, the LSP frequencies of order p can be obtained from this spectral difference. In this case, we derive the expression governing the pth order LSP frequencies. The efficient search for finding the LSP frequencies of order p can be done by proving the property that the LSP frequencies of order p and p-1 are interlaced with each other.

• Journal of Astronomy and Space Sciences
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• v.32 no.4
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• pp.341-348
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• 2015

New observations for the times of minimum lights of a well-known apsidal motion star CW Cephei were made using a 0.6 m wide field telescope at Jincheon station of Chungbuk National University Observatory, Korea during the 2015 observational season. We determined new times of minimum lights from these observations and analyzed O-C diagrams together with collected times of minima to study both the apsidal motion and the Light Time Effect (LTE) suggested in the system. The new periods of the apsidal motion and the LTE were calculated as 46.6 and 39.3 years, respectively, which were similar but improved accuracy than earlier ones investigated by Han et al. (2002), Erdem et al. (2004) and Wolf et al. (2006).

• Journal of Electrical Engineering and Technology
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• v.4 no.3
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• pp.337-345
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• 2009

Deregulation in power industry has made the reactive power ancillary service management a critical task to power system operators from both technical and economic perspectives. Reactive power management in power systems is a complex combinatorial optimization problem involving nonlinear functions with multiple local minima and nonlinear constraints. This paper proposes a practical market-based reactive power ancillary service management scheme to tackle the challenge. In this paper a new model for voltage security and reactive power management is presented. The proposed model minimizes reactive support cost as an economic aspect and insures the voltage security as a technical constraint. For modeling validation study, two optimization algorithm, a genetic algorithm (GA) and particle swarm optimization (PSO) method are used to solve the problem of optimum allocation of reactive power in power systems under open market environment and the results are compared. As a case study, the IEEE-30 bus power system is used. Results show that the algorithm is well competent for optimal allocation of reactive power under practical constraints and price based conditions.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.421-424
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• 1998

In this paper, a new on-line local path planning algorithm without local minima problem is proposed. This method, called Window Analysis Method (WAM), is simple and fast, and it helps a robot take a safe path avoiding obstacles in unknown environment. WAM has simulated on the mobile robot to demonstrate its reliability and fesibility.

• Journal of the Korean Society for Nondestructive Testing
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• v.12 no.1
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• pp.9-15
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• 1992

Ultrasonic spectroscopy is likely to become a very powerful NDE method for detection of microfects and thickness measurement of thin film below the limit of ultrasonic distance resolution in the opaque materials, provides a useful information that cannot be obtained by a conventional ultrasonic measuring system. In this paper, we considered a thin film below the limit of ultrasonic distance resolution sandwitched between two substances as acoustical analysis model, demonstrated the usefulness of ultrasonic spectroscopic analysis technique using information of ultrasonic frequency for measurements of thin film thickness, regardless of interference phenomenon and phase reversion of ultrasonic waveform. By using frequency intervals(${\triangle}f$) of periodic minima from the ratio of reference power spectrum of reflective waveform obtained a sample to power spectrum of multiple reflective waves obtained interference phenomenon caused by ultrasonic waves reflected at the upper and lower surfaces of a thin layer, can measured even dimensions of interest are smaller than the ultrasonic wave length with simplicity and accuracy.

• Management & Information Systems Review
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• v.2
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• pp.75-93
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• 1998

In this paper, we propose a new algorithm(N_BP) to be capable of overcoming limitations of the traditional backpropagation(O_BP). The N_BP is based on the method of conjugate gradients and calculates learning parameters through the line search which may be characterized by order statistics and golden section. Experimental results showed that the N_BP was definitely superior to the O_BP with and without a stochastic term in terms of accuracy and rate of convergence and might surmount the problem of local minima. Furthermore, they confirmed us that the stagnant phenomenon of learning in the O_BP resulted from the limitations of its algorithm in itself and that unessential approaches would never cured it of this phenomenon.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.107-112
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• 1998

In this paper, we propose a new paradigm (NEW_BP) to be capable of overcoming limitations of the traditional backpropagation(OLD_BP). NEW_BP is based on the method of conjugate gradients with the normalized direction vectors and computes step size through the linear search which may be characterized by order statistics and golden section. Simulation results showed that NEW_BP was definitely superior to both the stochastic OLD_BP and the deterministic OLD_BP in terms of accuracy and rate of convergence and might sumount the problem of local minima. Furthermore, they confirmed us that stagnant phenomenon of training in OLD_BP resulted from the limitations of its algorithm in itself and that unessential approaches would never cured it of this phenomenon.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.118-121
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• 1998

In this paper, we propose another paradigm(QNBP) to be capable of overcoming Limitations of the traditional backpropagation(SDBP). QNBPis based on the method of Quasi -Newton(variable metric) with the nomalized direction vectors and computes step size through the linear search. Simulation results showed that QNBP was definitely superior to both the stochasitc SDBP and the deterministic SDBP in terms of accuracy and rate of convergence and might sumount the problem of local minima. and there was no different between DFP+SR1 and BFGS+SR1 combined algrothms in QNBP.