• Computational Structural Engineering
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• v.9 no.1
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• pp.141-149
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• 1996

Efficient approximate reanalysis techniques based on substructuring are presented. In most optimal design problems, the analysis precedure must be repeated many times. In particular, one of the main obstacles in the structural optimization systems is high computational cost and time required for the repeated analysis of large-scale structural systems. The purpose of this paper is to show how to evaluate efficiently the sturctural behavior of new designs using information from the previous ones, instead of the multiple repeated analysis of basic equations for successive modification in the optimal design. The proposed reanalysis method is a combined Taylor series expansion and reduced basis method based on substructuring. Several numerical examples illustrate the effectiveness of the method.

• Geophysics and Geophysical Exploration
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• v.20 no.2
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• pp.96-99
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• 2017

Virtual source data were produced by applying the seismic interferometry to the 2002 experimental seismic refraction data. Using the data, moveout velocities and effective anellipticity were experimentally computed for the crust at eight sites in the Korean peninsula. The moveout velocities of reflection events at approximate Moho depths were yielded to be $6.30{\pm}0.25km/s$ using near-offset traveltimes. Expanding the Taylor approximation to the $3^{rd}$ term for far-offset traveltimes, the effective anellipticity parameters were computed to be $0.18{\pm}0.07$ for the crust material.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.11
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• pp.1681-1690
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• 2013

In this paper, a design of speed and position controller based on the EKF(Extended Kalman Filter) for sensorless control in IPMSM(Interior Permanent Magnet Synchronous Motor) is proposed. The proposed method subdivides the state estimation interval for improving the accuracy of state estimation. and each subdivided interval estimated first order term using Taylor series. The proposed state estimator comparison with the second-order extended Kalman filter reduced calculation amount of a priori estimation. And the simulation results were proved that The accuracy of priori estimation is increased.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.320-323
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• 2010

This paper proposes efficient log and exponent calculation methods using a dual phase instruction set without additional ALU unit for a mobile enviroment. Using the Dual Phase Instruction set, it extracts exponent and mantissa from expression of floating point and calculates 24bit single precision floating point of log approximation using the Taylor series expansion algorithm. And with dual phase instruction set, it reduces instruction excution cycles. The proposed Dual Phase architecture reduces the performance degradation and maintain smaller size.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.3
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• pp.127-132
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• 2018

In this paper, a scheme for the evaluation of variability in the eigen-modes of functionally graded material(FGM) beams is proposed within the framework of perturbation-based stochastic analysis. As a random parameter, the spatially varying elastic modulus of FGM along the axial direction at the mid-surface of the beam is chosen, and the thru-thickness variation of the elastic modulus is assumed to follow the original form of exponential variation. In deriving the formulation, the first order Taylor expansion on the eigen-modes is employed. As an example, a simply supported FGM beam having symmetric elastic modulus with respect to the mid-surface is chosen. Monte Carlo analysis is also performed to check if the proposed scheme gives reasonable outcomes. From the analyses it is found that the two schemes give almost identical results of the mean and standard deviation of eigen-modes. With the propose scheme, the standard deviation shape of respective eigen-modes can be evaluated easily. The deviated mode shape is found to have one more zero-slope points than the mother modes shapes, irrespective of order of modes. The amount of deviation from the mean is found to have larger values for the higher modes than the lower modes.

• Geophysics and Geophysical Exploration
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• v.16 no.2
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• pp.71-78
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• 2013

The one-way wave equation migration is much more computationally efficient comparing with reverse time migration and it can provide better image than the migration algorithm based on the ray theory. We have developed the prestack depth migration module adopting (GS) propagator designed for vertical transverse isotropic media. Since GS propagator considers the higher-order term by expanding the Taylor series of the vertical slowness in the thin slab of the phase-screen propagator, the GS migration can offer more correct image for the complex subsurface with large lateral velocity variation or steep dip. To verify the validity of the developed GS migration module, we analyzed the accuracy with the order of the GS propagator for VTI media (GSVTI propagator) and confirmed that the accuracy of the wavefield propagation with the wide angles increases as the order of the GS propagator increases. Using the synthetic seismic data, we compared the migration results obtained from the isotropic GS migration module with the anisotropic GS migration module. The results show that the anisotropic GS migration provides better images and the improvement is more evident on steeply dipping structures and in a strongly anisotropic medium.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.155-163
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• 2012

The geometrical and electrical errors of array sensors can severely degrade the performance of array sensor system. Various calibration techniques are developed to alleviate this problem. In this paper, two different calibration methods with respect to location, gain and phase of array sensors are presented. One method applies the first-order Taylor series expansion to approximate the true steering vector from the nominal values of array sensors. Then a set of equations is formed by using the null characteristics of the MUSIC spectrum to estimate errors of location, gain and phase of array sensors. Another method estimates these errors based on the data covariance matrix of pilot sources. From the simulations, it is demonstrated that two calibration algorithms calibrated an array system successfully. In addition to that, Fistas and Manikas's algorithm is more robust against noise than Ng and Lie's one when SNR is from 10dB to 50dB.

• The Korean Journal of Applied Statistics
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• v.21 no.2
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• pp.327-340
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• 2008

This paper derives joint and conditional Lagrange multiplier tests based on information matrix for testing functional form and/or the presence of autocorrelation in a regression model. Small sample properties of these tests are assessed by Monte Carlo study and comparisons are made with LM tests based on Hessian matrix. The results show that the proposed $LM_E$ tests have the most appropriate finite sample performance.

• Journal of Korea Technology Innovation Society
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• v.9 no.1
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• pp.175-198
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• 2006

Analyzing the effects of information technology(IT) in the life insurance Industry is important in establishing the direction for future information technology investment. In this research, the cost-elasticity of IT capital stock was measured by the SUR technique, using the second-order translog cost function, which was drawn out by a Taylor expansion of the multi-product joint cost function. Analysis was made based on data from 1991 to 2003 collected from 33 life insurance firms. The results show that although the effects of information technology investment vary according to individual life insurance firms, half of the life insurance firms surveyed reduced their costs by investing in information technology. The research also revealed that although large life insurance firms reduced their costs by investing in information technology medium & small life insurance firms and foreign ,life insurance firms increase their costs. Additionally, although both information capital and information labor increase as the information budget increases, the increase in information capital is larger than one in information labor. Because the price of information capital is decreased rapidly more than one of information-related labor.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.2
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• pp.53-58
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• 1998

Ekman layer equation with rough-bottom boundary condition has been solved to determine the effect of roughness on the magnitude of Ekman veering. The bottom boundary condition and the flow field were expanded in a power of roughness (h) which is always smaller than the Ekman layer thickness (${\delta}_E$). By changing the magnitude of roughness parameter (h/${\delta}_E$), the magnitude of the veering, which rotates counterclockwise from the interior geostrophic flow, has been computed. At a fixed depth within the Ekman layer, the magnitude of veering increases as the roughness parameter increases. However, the cross-isobar flux turns out to decrease with increasing roughness. To verify the analytic solution, laboratory experiments were carried out. Rough-bottom cylinderical container filled with homogeneous fluid was sit on a rotating table. The flow pattern during the period of steady spin-up shows that the degree of veering coincides well with the analytic results for various roughness parameters.