• Title/Summary/Keyword: Error Source

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Evaluation of Inverse Fourier Integral Considering the Distances from the Source Point in 2D Resistivity Modeling (전기비저항탐사 2차원 모델링에서 송수신 간격을 고려한 푸리에 역변환)

  • Cho, In-Ky;Jeong, Da-Bhin
    • Geophysics and Geophysical Exploration
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    • v.21 no.1
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    • pp.1-7
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    • 2018
  • In the two-dimensional (2D) modeling of electrical method, the potential in the space domain is reconstructed with the calculated potentials in the wavenumber domain using inverse Fourier transform. The inverse Fourier integral is numerically evaluated using the transformed potential at different wavenumbers. In order to improve the precision of the integration, either the logarithmic or exponential approximation has been used depending on the size of wavenumber. Two numerical methods have been generally used to evaluate the integral; interval integration and Gaussian quadrature. However, both methods do not consider the distance from the current source. Thus the resulting potential in the space domain shows some error. Especially when the distance from the current source is very small or large, the error increases abruptly and the evaluated potential becomes extremely unstable. In this study, we developed a new method to calculate the integral accurately by introducing the distance from the current source to the rescaled Gauss abscissa and weight. The numerical tests for homogeneous half-space model show that the developed method can yield the error level lower than 0.4 percent over the various distances from the current source.

Optimization of color filters selection to estimate surface spectral reflectance of Munsell colors (물체의 분광반사율 추정을 위한 최적필터의 선정)

  • 이승희;이을환;유미옥;노상철;안석출
    • Journal of the Korean Graphic Arts Communication Society
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    • v.16 no.3
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    • pp.121-131
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    • 1998
  • The object color does not look same under the different light source. It depends on the surface spectral reflectance and the spectral distribution of light source. Therefore we should find the surface spectral reflectance of object color and the spectral distribution of light source for color reproduction. Using Wiener estimation, we can estimate the spectral reflectance from low dimensional images obtained with multi-band image acquisition system. The kind and the number of imaging filters have the effect on the estimation of the spectral reflectance. Therefore it is important that optimal filters are selected to minimize the error of the result. In this paper, we describe methods to select optimal filters with minimum error between measured and estimated surface spectral reflectance and to estimate surface spectral reflectance of Munsell color chart from six multi-band images by using Wiener estimation.

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Error Analysis Caused by Using the Dftin Numerical Evaluation of Rayleigh's Integral (레일리 인테그랄의 수치해석상 오차에 대한 이론적 고찰)

  • Kim, Sun-I.
    • Journal of Biomedical Engineering Research
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    • v.10 no.3
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    • pp.323-330
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    • 1989
  • Large bias errors which occur during a numerical evaluation of the Rayleigh's integral is not due to the replicated source problem but due to the coincidence of singularities of the Green's function and the sampling points in Fourier domain. We found that there is no replicated source problem in evaluating the Rayleigh's integral numerically by the reason of the periodic assumption of the input sequence in Dn or by the periodic sampling of the Green's function in the Fourier domain. The wrap around error is not due to an overlap of the individual adjacent sources but berallse of the undersampling of the Green's function in the frequency domain. The replicated and overlApped one is inverse Fourier transformed Green's function rather than the source function.

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Variance Analysis for State Estimation In Communication Channel with Finite Bandwidth (유한한 대역폭을 가지는 통신 채널에서의 상태 추정값에 대한 분산 해석)

  • Fang, Tae-Hyun;Choi, Jae-Weon
    • Proceedings of the KSME Conference
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    • 2000.11a
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    • pp.693-698
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    • 2000
  • Aspects of classical information theory, such as rate distortion theory, investigate how to encode and decode information from an independently identically distributed source so that the asymptotic distortion rate between the source and its quantized representation is minimized. However, in most natural dynamics, the source state is highly corrupted by disturbances, and the measurement contains the noise. In recent coder-estimator sequence is developed for state estimation problem based on observations transmitted with finite communication capacity constraints. Unlike classical estimation problems where the observation is a continuous process corrupted by additive noises, the condition is that the observations must be coded and transmitted over a digital communication channel with finite capacity. However, coder-estimator sequence does not provide such a quantitative analysis as a variance for estimation error. In this paper, under the assumption that the estimation error is Gaussian distribution, a variance for coder-estimation sequence is proposed and its fitness is evaluated through simulations with a simple example.

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Design of Rogowski coil to improve of current measurement sensitivity (전류측정감도 개선을 위한 로고우스키 코일의 설계)

  • Park, J.N.;Lee, C.;Jang, Y.M.;Kang, S.H.;Lim, K.J.;Na, D.H.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11b
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    • pp.609-612
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    • 2001
  • Rogowski coil is made having no ferromagnetic material in a core. So the coil cannot be driven into saturation. This result in that Rogowski coils may be calibrated at relatively low currents. and used with confidence at very high currents. However the lowest level of current that can be measured is limited by the sensitivity of the voltage measuring instrument and system noise. Therefore. geometrical effects were investigated in order to measure high sensitivity of low level current and the significant source of error was examined as well. In the results, the source of error was associated with coil designs. i.e. shape and uniformity of coil and a geometrical location of current source inside and outside of the Rogowski coil.

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Experimental Study on Performance Tests of Vibration Source for Helical Gears (헬리컬 기어계의 가진원 성능 평가에 대한 실험적 연구)

  • Park, Gwang-Min;Kim, Chan-Jung;Lee, Jae-won;Lee, Bong-Hyun;Kim, Wan-soo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2014.10a
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    • pp.602-603
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    • 2014
  • A gearbox can be regarded as a self-exciting dynamic system, which has a vibration source. Transmission error (TE) is considered to be an main excitation source for gear noise and vibration. The TE excitation is transmitted through the gears, shafts, bearings, and housings. Thus, an experimental approach to each mechanical parts is useful in order to understand and evaluate the dynamic behaviour of a gearbox. This study is focused on the transmission and vibration characteristics of a helical gear system in development stage. In addition, by considering the tolerance factors and resonance characteristics, the vibration response of actual dynamic system is analysed.

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Spectral Features of Seismic Wave Propagation from Odaesan Earthquake (M=4.8, '07. 1. 20) (오대산지진(M=4.8, '07. 1. 20)의 지진파 전달특성 평가)

  • Yun, Kwan-Hee;Park, Dong-Hee;Chang, Chung-Joong
    • 한국지구물리탐사학회:학술대회논문집
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    • 2007.06a
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    • pp.81-86
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    • 2007
  • Spectral features of the seismic wave propagation from Odaesan Earthquake were evaluated based on the commonly treated random error between the observed data and the prediction values by the stochastic point-source ground-motion spectral model regarding the source, path and site effects. Radiation pattern of the error according to azimuth angle was found to be similar to the theoretical estimate. It was also observed that the spatial distribution of the errors was correlated with the geological map and the Q0 map which are indicatives of seismic boundaries.

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Optimization of color filters selection to estimate surface spectral reflectance of Munsell colors (물체의 분광반사 추정을 위한 최적필터의 선정)

  • 이승희;김종필;이을환;노상철;안석출
    • Proceedings of the Korean Printing Society Conference
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    • 1998.10a
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    • pp.1-6
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    • 1998
  • The object color does not look same under the different light source. It depends on the surface spectral reflectance and the spectral distribution of light source. Therefore we should find the surface spectral reflectance of object color and the spectral distribution of light source for color reproduction. Using Winer estimation, we can reconstruct the spectral reflectance from low dimensional images obtained with a few filters. The kind and the number of filters have the effect on the estimation of the spectral reflectance. Therefore it is important that optimal filters are selected to minimize the error of the result. In this paper, we describe methods to select optimal filters with minimum error between measured and estimated surface spectral reflectance and to estimate surface spectral reflectance of Munsell color from six band images by using Wiener estimation.

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Secure Transmission for Two-Way Vehicle-to-Vehicle Networks with an Untrusted Relay

  • Gao, Zhenzhen
    • IEIE Transactions on Smart Processing and Computing
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    • v.4 no.6
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    • pp.443-449
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    • 2015
  • This paper considers the physical layer security problem for a two-way vehicle-to-vehicle network, where the two source vehicles can only exchange information through an untrusted relay vehicle. The relay vehicle helps the two-way transmission but also acts as a potential eavesdropper. Each vehicle has a random velocity. By exploiting the random carrier frequency offsets (CFOs) caused by random motions, a secure double-differential two-way relay scheme is proposed. While achieving successful two-way transmission for the source vehicles, the proposed scheme guarantees a high decoding error floor at the untrusted relay vehicle. Average symbol error rate (SER) performance for the source vehicles and the untrusted relay vehicle is analyzed. Simulation results are provided to verify the proposed scheme.

Design of Rogowski coil to improve of current measurement sensitivity (전류측정감도 개선을 위한 로고우스키 코일의 설계)

  • Park, J. N.;Lee, C.;Jang, Y. M.;Kang, S. H.;Lim, K. J.;Na, D. H.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • 2001.11a
    • /
    • pp.609-612
    • /
    • 2001
  • Rogowski coil is made having no ferromagnetic material in a core. So the coil cannot be driven into saturation. This result in that Rogowski coils may be calibrated at relatively low currents, and used with confidence at very high currents. However the lowest level of current that can be measured is limited by the sensitivity of the voltage measuring instrument and system noise. Therefore, geometrical effects were investigated in order to measure high sensitivity of low level current and the significant source of error wa examined as well. n the results, the source of error was associated with coil designs, i.e. shape and uniformity of coil and a geometrical location of current source inside and outside of the Rogowski coil.

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