• Title/Summary/Keyword: Spatial averaging

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Validation of Assessment for Mean Flow Field Using Spatial Averaging of Instantaneous ADCP Velocity Measurements (ADCP 자료의 공간평균을 이용한 평균유속장 산정에 대한 검증)

  • Kim, Dong-Su;Kang, Boo-Sik
    • Journal of Environmental Science International
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    • v.20 no.1
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    • pp.107-118
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    • 2011
  • While the assessment of mean flow field is very important to characterize the hydrodynamic aspect of the flow regime in river, the conventional methodologies have required very time-consuming efforts and cost to obtain the mean flow field. The paper provides an efficient technique to quickly assess mean flow field by developing and applying spatial averaging method utilizing repeatedly surveyed acoustic Doppler current profiler(ADCP)'s cross-sectional measurements. ADCP has been widely used in measuring the detailed velocity and discharge in the last two decades. In order to validate the proposed spatial averaging method, the averaged velocity filed using the spatial averaging was compared with the bench-mark data computed by the time-averaging of the consistent fix-point ADCP measurement, which has been known as a valid but a bit inefficient way to obtain mean velocity field. The comparison showed a good agreement between two methods, which indicates that the spatial averaging method is able to be used as a surrogate way to assess the mean flow field. Bed shear stress distribution, which is a derived hydrodynamic quantity from the mean velocity field, was additionally computed by using both spatial and time-averaging methods, and they were compared each other so as to validate the spatial averaging method. This comparison also gave a good agreement. Therefore, such comparisons proved the validity of the spatial averaging to quickly assess mean flow field. The mean velocity field and its derived riverine quantities can be actively used for characterizing the flow dynamics as well as potentially applicable for validating numerical simulations.

2-Dimensional Spatial Averaging Driving Methods for High Speed Driving of AMLCDs

  • You, Bong-Hyun;Lee, Jun-Pyo;Kim, Dong-Gyu;Park, Jin-Ho;Kim, Yun-Jae;Berkeley, Brian H.;Kim, Sang-Soo
    • 한국정보디스플레이학회:학술대회논문집
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    • 2007.08b
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    • pp.1323-1326
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    • 2007
  • A new driving method employing 2-dimensional spatial averaging is proposed. This method successfully eliminates the vertical line artifact caused by luminance difference from unbalanced charging voltage between polarities. This spatial averaging method can secure charging time, minimize driver heating, and achieve higher display quality.

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THE EIGENVALUE PROBLEM AND A WEAKER FORM OF THE PRINCIPLE OF SPATIAL AVERAGING

  • Kwean, Hyuk-Jin
    • The Pure and Applied Mathematics
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    • v.9 no.1
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    • pp.31-37
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    • 2002
  • In this paper, we find explicitly the eigenvalues and the eigenfunctions of Laplace operator on a triangle domain with a mixed boundary condition. We also show that a weaker form of the principle of spatial averaging holds for this domain under suitable boundary condition.

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Effect of Spatial Distribution of Material Properties on its Experimental Estimation (재질의 공간적 변동이 재료강도시험결과에 미치는 영향)

  • Kim, S.J.
    • Journal of Power System Engineering
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    • v.4 no.2
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    • pp.40-45
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    • 2000
  • Some engineering materials are often known to have considerable spatial variation in their resisting strength and other properties. The objective of this study is to investigate the averaging effect and the applicability of extremal statistic for the statistical size effect. In the present study, it is assumed that the material property is a stationary random process in space. The theoretical autocorrelation function of the material strength are discussed for several correlation lengths. And, in order to investigate the statistical size effect, the material properties was simulated by using the non-Gaussian random process method. The material properties were plotted on the Weibull probability papers. The main results are summarized as follows: The autocorrelation function of the material properties are almost independent of the averaging length. The variance decreases with increasing the averaging length. As correlation length is smaller, the slope is larger. And also, it was found that Weibull statistics based on the weakest-link model could not explain the spatial variation of material properties with respect to the size effect satisfactory.

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A GEOMETRIC CRITERION FOR THE WEAKER PRINCIPLE OF SPATIAL AVERAGING

  • Kwean, Hyuk-Jin
    • Communications of the Korean Mathematical Society
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    • v.14 no.2
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    • pp.337-352
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    • 1999
  • In this paper we find a geometric condition for the weaker principle of spatial averaging (PSA) for a class of polyhedral domains. Let \ulcorner be a polyhedron in R\ulcorner, n$\leq$3. If all dihedral angles of \ulcorner are submultiples of $\pi$, then there exists a parallelopiped \ulcorner generated by n linearily independent vectors {\ulcorner}\ulcorner in R\ulcorner containing \ulcorner so that solutions of $\Delta$u+λu=0 in \ulcorner with either the boundary condition u=0 or ∂u/∂n=0 are expressed by linear combinations of those of $\Delta$u+λn=0 in \ulcorner with periodic boundary condition. Moreover, if {\ulcorner}\ulcorner satisfies rational condition, we guarantee the weaker PSA for the domain \ulcorner.

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Spatially Close Signals Separation via Array Aperture Expansions and Spatial Spectrum Averaging

  • Kang, Heung-Yong;Kim, Young-Su;Kim, Chang-Joo
    • ETRI Journal
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    • v.26 no.1
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    • pp.45-47
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    • 2004
  • A resolution enhancement method for estimating the direction-of-arrival (DOA) of signals is presented. The proposed method is by virtually expanding a real array into virtual arrays and then averaging the spatial spectrum of the virtual arrays, each of which has a different aperture size. Superior DOA resolutions are shown in comparison with the standard algorithm, MUltiple SIgnal Classification (MUSIC), for incoherent signals incident on a uniform circular array.

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Evaluation of spatial pressure distribution during ice-structure interaction using pressure indicating film

  • Kim, Hyunwook;Ulan-Kvitberg, Christopher;Daley, Claude
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.6 no.3
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    • pp.578-597
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    • 2014
  • Understanding of 'spatial' pressure distribution is required to determine design loads on local structures, such as plating and framing. However, obtaining a practical 'spatial' pressure distribution is a hard task due to the sensitivity of the data acquisition frequency and resolution. High-resolution Pessure-Idicating Flm (PIF) was applied to obtain pressure distribution and pressure magnitude using stepped crushing method. Different types of PIF were stacked at each test to creating a pressure distribution plot at specific time steps. Two different concepts of plotting 'spatial' pressure-area curve was introduced and evaluated. Diverse unit pixel size was chosen to investigate the effect of the resolution in data analysis. Activated area was not significantly affected by unit pixel size; however, total force was highly sensitive.

Reliability Analysis of Slope Stability with Sampling Related Uncertainty (통계오차를 고려한 사면안정 신뢰성 해석)

  • Kim, Jin-Man
    • Journal of the Korean Geotechnical Society
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    • v.23 no.3
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    • pp.51-59
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    • 2007
  • A reliability-based approach that can systematically model various sources of uncertainty is presented in the context of slope stability. Expressions for characterization of soil properties are developed in order to incorporate sampling errors, spatial variability and its effect of spatial averaging. Reliability analyses of slope stability with different statistical representations of soil properties show that the incorporation of sampling error, spatial correlation, and conditional simulation leads to significantly lower probability of failure than that obtained by using simple random variable approach. The results strongly suggest that the spatial variability and sampling error have to be properly incorporated in slope stability analysis.

A study on enhancement of heterogeneous noisy image quality for the performance improvement of target detection and tracking (표적 탐지/추적 성능 향상을 위한 불균일 미세 잡음 영상 화질개선 연구)

  • Kim, Y.;Yoo, P.H.;Kim, D.S.
    • Journal of Korea Multimedia Society
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    • v.17 no.8
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    • pp.923-936
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    • 2014
  • Images can be contaminated with different types of noise, for different reasons. The neighborhood averaging and smoothing by image averaging are the classical image processing techniques for noise removal. The classical spatial filtering refers to the aggregate of pixels composing an image and operating directly on these pixels. To reduce or remove effectively noise in image sequences, it usually needs to use noise reduction filter based on space or time domain such as method of spatial or temporal filter. However, the method of spatial filter can generally cause that signals of objects as the target are also blurred. In this paper, we propose temporal filter using the piece-wise quadratic function model and enhancement algorithm of image quality for the performance improvement of target detection and tracking by heterogeneous noise reduction. Image tracking simulation that utilizes real IIR(Imaging Infra-Red) images is employed to evaluate the performance of the proposed image processing algorithm.