• 대한전기학회논문지
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• 제45권3호
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• pp.399-406
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• 1996

This paper presents a method of hierarchical state estimation of the time-varying linear systems via Block-pulse function(BPF). When we estimate the state of the systems where noise is considered, it is very difficult to obtain the solutions because minimum error variance matrix having a form of matrix nonlinear differential equations is included in the filter gain calculation. Therefore, hierarchical approach is adapted to transpose matrix nonlinear differential equations to a sum of low order state space equation from and Block-pulse functions are used for solving each low order state space equation in the form of simple and recursive algebraic equation. We believe that presented methods are very attractive nd proper for state estimation of time-varying linear systems on account of its simplicity and computational convenience. (author). 13 refs., 10 figs.

• 한국군사과학기술학회지
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• 제9권2호
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• pp.152-160
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• 2006

Time marching methods are well-suited for high speed compressible flow computations. However, it is well known that the time marching methods suffer a slow down in convergence due to disparity in Eigenvalues. A local preconditioning method is one of numerical methods to enhance convergence characteristics of low mach number flows by modifying Eigenvalues of the governing equations. In this paper, the local preconditioning method of Weiss is applied to a 2 dimensional Navier-Stokes code and the efficiency of the preconditioning method is shown through a number of computational examples.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.5063-5073
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• 2016

In this paper, an efficient texture compression method is proposed for fast rendering, which exploits the spatial correlation among blocks through intra-picture block matching. Texture mapping is widely used to enhance the visual quality of results in real-time rendering applications. For fast texture mapping, it is necessary to identify an effective trade-off between compression efficiency and computational complexity. The conventional compression methods utilized for image processing (e.g., JPEG) provide high compression efficiency while resulting in high complexity. Thus, low complexity methods, such as ETC1, are often used in real-time rendering applications. Although these methods can achieve low complexity, the compression efficiency is still lower than that of JPEG. To solve this problem, we propose a texture compression method by reducing the spatial redundancy between blocks in order to achieve the better compression performance than ETC1 while maintaining complexity that is lower than that of JPEG. Experimental results show that the proposed method achieves better compression efficiency than ETC1, and the decoding time is significantly reduced compared to JPEG while similar to ETC1.

• IEIE Transactions on Smart Processing and Computing
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• 제4권4호
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• pp.237-250
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• 2015

This paper describes a hardware-oriented algorithm and its conceptual implementation in a real-time speed limit traffic sign detection system on an automotive-oriented field-programmable gate array (FPGA). It solves the training and color dependence problems found in other research, which saw reduced recognition accuracy under unlearned conditions when color has changed. The algorithm is applicable to various platforms, such as color or grayscale cameras, high-resolution (4K) or low-resolution (VGA) cameras, and high-end or low-end FPGAs. It is also robust under various conditions, such as daytime, night time, and on rainy nights, and is adaptable to various countries' speed limit traffic sign systems. The speed limit traffic sign candidates on each grayscale video frame are detected through two simple computational stages using global luminosity and local pixel direction. Pipeline implementation using results-sharing on overlap, application of a RAM-based shift register, and optimization of scan window sizes results in a small but high-performance implementation. The proposed system matches the processing speed requirement for a 60 fps system. The speed limit traffic sign recognition system achieves better than 98% accuracy in detection and recognition, even under difficult conditions such as rainy nights, and is implementable on the low-end, low-cost Xilinx Zynq automotive Z7020 FPGA.

• 한국정보과학회논문지:소프트웨어및응용
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• 제32권4호
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• pp.277-289
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• 2005

선택과 재생산을 특징으로 하는 계통적 학습에서 유전자 프로그램이 가지는 긴 설계시간/높은 계산노력/낮은 계산효율을 극복하고자, 이 논문은 XML에 기반을 둔 유전적 표현 방법을 제안한다. 이 방법에서 유전자 프로그램과 유전자 연산은 기성 DOM 파서의 API 호출에 의하여 관리되기 때문에, 유전자 프로그램을 설계하는데 소비되는 시간이 상당히 단축되는 특징이 있다. 또 표준 XML 스키마를 기반으로 의미적으로 올바른 유전자 프로그램만을 다루기 때문에 탐색공간과 계산노력이 감소된다. 그리고 이형 분산 컴퓨팅 환경에서 유전자 프로그램의 이주에 적합한 시스템 및 형식인 XML을 사용하기 때문에 유전자 프로그램이 병렬적으로 수행될 수 있고, 이에 따라 계산효율이 향상된다. 제안된 방법의 검증을 위하여 포식자-피식자 문제에서 다중 에이전트의 사회적 행동의 진화에 적용한 결과, 유전자 프로그램에 대한 계산시간이 단축됨을 .보인다

• 대한임베디드공학회논문지
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• 제13권1호
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• pp.1-8
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• 2018

This paper proposes a low complexity super resolution algorithm for frequency modulated continuous wave (FMCW) radar systems for foreign object debris (FOD) detection. FOD radar has a requirement to detect foreign object in small units in a large area. However, The fast Fourier transform (FFT) method, which is most widely used in FMCW radar, has a disadvantage in that it can not distinguish between adjacent targets. Super resolution algorithms have a significantly higher resolution compared with the detection algorithm based on FFT. However, in the case of the large number of samples, the computational complexity of the super resolution algorithms is drastically high and thus super resolution algorithms are difficult to apply to real time systems. In order to overcome this disadvantage of super resolution algorithm, first, the proposed algorithm coarsely obtains the frequency of the beat signal by employing FFT. Instead of using all the samples of the beat signal, the number of samples is adjusted according to the frequency of the beat signal. By doing so, the proposed algorithm significantly reduces the computational complexity of multiple signal classifier (MUSIC) algorithm. Simulation results show that the proposed method achieves accurate location even though it has considerably lower complexity than the conventional super resolution algorithms.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
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• pp.497-504
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• 1998

In the nonlinear dynamic structural analysis, the given ground excitation as an input should be well defined. Because of the lack of recorded accelerograms in Korea, it is required to generate an artificial earthquake by a stochastic model of ground excitation with various dynamic properties rather than recorded accelerograms. It is well own that earthquake motions are generally non-stationary with time-varying intensity and frequency content. Many researchers have proposed non-stationary random process models. Yeh and Wen (1990) proposed a non-stationary stochastic process model which can be modeled as components with an intensity function, a frequency modulation function and a power spectral density function to describe such non-stationary characteristics. This model is based on the simulation for the strong-motion earthquakes with magnitude greater than approximately 5.0~6.0, because it will be not only expected to cause structural damage but also involved the characteristics of earthquake motions. Also, the recorded earthquake motion within this range are still very scarce in Korea. Thus, it is necessary to verify the model by the application of it to the mid-magnitude (approximately 4.0~6.0) earthquakes actually recorded in domestic or foreign area. The purpose of the paper is to generate an artificial earthquake using the model of Yeh and Wen in the area with low seismicity.

• 한국통신학회논문지
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• 제22권4호
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• pp.648-661
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• 1997

This paper presents a new method for post-processing of coded images based upon the low-pass filtering followed by the projection onto the NQCS (narrow quantization constraint set). We also investigate how the proposed method works on JPEG-coded real images. The starting point of the QCS-based post-processing techniques is the centroid of the QCS, where the original image belongs. The low-pass filtering followed by the projection onto the QCS makes the images lie on the boundary of the QCS. It is likely that, however, the original image is inside the QCS. Hence projection onto the NQCS gives a lower MSE (mean square error) than does the projection onto the QCS. Simulation results show that setting the narrowing coefficients of the NQCS to be 0.2 yields the best performance in most cases. Even though the JPEG-coded image is low-pass filtered and projected onto the NQCS repeatedly, there is no guarantee that the resultant image has a lower MSE and goes closer to the original image. Thus only one iteration is sufficient for the post-processing of the coded images. This is interesting because the main drawback of the iterative post-processing techniques is the heavy computational burden. The single iteration method reduces the computational burden and gives us an easy way to implement the real time VLSI post-processor.

• 대한기계학회논문집B
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• 제22권2호
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• pp.240-252
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• 1998

The purpose of this study is to develop a method for predicting the aerodynamic performance of the low speed airfoils in the 2-dimensional, steady and viscous flow. For this study, the airfoil geometry is specified by adopting the longest chord line system and by considering local surface curvature. In case of the inviscid incompressible flow, the analysis is accomplished by the linearly varying strength vortex panel method and the Karman-Tsien correction law is applied for the inviscid compressible flow analysis. The Goradia integral method is adopted for the boundary layer analysis of the laminar and turbulent flows. Viscous and inviscid solutions are converged by the Lockheed iterative calculating method using the equivalent airfoil geometry. The analysis of the separated flow is performed using the Dvorak and Maskew's method as the basic method. The wake effect is also considered by expressing its geometry using the formula of Summey and Smith when no separation occurs. The computational efficiency is verified by comparing the computational results with experimental data and by the shorter execution time.

• 한국전자파학회논문지
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• 제13권2호
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• pp.217-224
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• 2002

FDTD 해석법에서 공간적 셀의 크기는 해석의 정확도를 결정하는 중요한 요소이다. 하지만 정확도를 향상시키기 위하여 진의 크기를 줄이게 되면, 해석시간과 기억용량의 증가를 초래하게 되는데 서브 그리딩을 사용하여 이를 해결할 수 있다. 본 논문에서는 관심영역만 세밀하게 해석할 수 있는 3차원 서브 그리딩법을 기술하고 이를 응용하여 몇 가지의 구조를 해석하였다. 제안한 방범의 타당성을 화인하기 위하여 균일 그리딩과 서브 그리딩을 적용하여 특성을 해석하고 그 격과를 비교하였다. 제안한 방법을 사용하였을 경우 동일한 정확도에서 균일 그리딩에 비하여 6배의 해석시간의 줄었고 기억용량은 2.5배 정도 줄어들었다.