• Journal of Korea Water Resources Association
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• v.38 no.6 s.155
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• pp.439-448
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• 2005

This paper introduces the wavelet transform that was improved by the fourier transform to assess periodicities and trends, we assessed propriety with examples of two monthly precipitation data, annual precipitation, SOI index and SST index. The wavelet transform can effectively assess the power spectrum corresponding to frequency as maintaining chronological characteristics. The results of the analysis using the wavelet transform showed that the monthly precipitation have the strongest power spectrum near that of 1 year, and the annual precipitation represent the dominated spectrum in the band of 2-8 years. Also, the SOI index and SST index indicate the strongest power spectrum in the band of 2-8 years.

• Structural Engineering and Mechanics
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• v.67 no.2
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• pp.185-206
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• 2018

This paper studies the non-axisymmetric 3D problem on the dynamics of the moving load acting in the interior of the hollow cylinder surrounded with elastic medium and this study is made by utilizing the exact equations of elastodynamics. It is assumed that in the interior of the cylinder the point located with respect to the cylinder axis moving forces act and the distribution of these forces is non-axisymmetric and is located within a certain central angle. The solution to the problem is based on employing the moving coordinate method, on the Fourier transform with respect to the spatial coordinate indicated by the distance of the point on the cylinder axis from the point at which the moving load acts, and on the Fourier series presentation of the Fourier transforms of the sought values. Numerical results on the critical moving velocity and on the distribution of the interface normal and shear stresses are presented and discussed. In particular, it is established that the non-axisymmetricity of the moving load can decrease significantly the values of the critical velocity.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1087-1090
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• 1996

The objective of this paper is to present a new input torque shaping method for slewing and vibration suppression of flexible structure based on Fourier series expansion. Vibration energy of the structure with shaped control input is investigated with respect to the shaping parameter of the reference torque, maneuver time and the number of trigonometric functions to be included in the series. Analytic expressions of the performance indices and their derivatives are derived in the modal coordinates. Numerical results show the effectiveness of the proposed approach to design the open-loop control law that modifies the shape of input torque for simultaneous slewing and vibration suppression.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.6
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• pp.529-534
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• 1988

This paper describes a new method to eliminate some selected harmonics in PWM waveforms using the Walsh series which substitute the linear algebraic equations for the nonlinear equations required in the Fourier series harmonic elimination. In addition, this method is simulated to synthesize periodic PWM waveforms and compare the Walsh analysis with the FOurier analysis, Experimental results are shown that a singel-phase PWM waveforms are identified with the proposed Walsh Series.

• Journal of Ocean Engineering and Technology
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• v.36 no.2
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• pp.101-107
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• 2022

Dean (1965) proposed the use of the root mean square error (RMSE) in the dynamic free surface boundary condition (DFSBC) and kinematic free-surface boundary condition (KFSBC) as an error evaluation criterion for wave theories. There are well known wave theories with RMSE more than 1%, such as Airy theory, Stokes theory, Dean's stream function theory, Fenton's theory, and trochodial theory for deep-water waves. However, none of them can be applied for deep-water breaking waves. The purpose of this study is to provide a closed-form solution for deep-water waves with RMSE less than 1% even for breaking waves. This study is based on a previous study (Shin, 2016), and all flow fields were simplified for deep-water waves. For a closed-form solution, all Fourier series coefficients and all related parameters are presented with Newton's polynomials, which were determined by curve fitting data (Shin, 2016). For verification, a wave in Miche's limit was calculated, and, the profiles, velocities, and the accelerations were compared with those of 5^th-order Stokes theory. The results give greater velocities and acceleration than 5^th-order Stokes theory, and the wavelength depends on the wave height. The results satisfy the Laplace equation, bottom boundary condition (BBC), and KFSBC, while Stokes theory satisfies only the Laplace equation and BBC. RMSE in DFSBC less than 7.25×10^-2% was obtained. The series order of the proposed method is three, but the series order of 5^th-order Stokes theory is five. Nevertheless, this study provides less RMSE than 5^th-order Stokes theory. As a result, the method is suitable for offshore structural design.

• JSTS:Journal of Semiconductor Technology and Science
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• v.1 no.4
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• pp.209-215
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• 2001

In this paper a method for analysis and modelling of coplanar transmission interconnect lines that are placed on top of silicon-silicon oxide substrates is presented. The potential function is expressed by series expansions in terms of solutions of the Laplace equation for each homogeneous region of layered structure. The expansion coefficients of different series are related to each other and to potentials applied to the conductors via boundary conditions. In the plane of conductors, boundary conditions are satisfied at $N_d$ discrete points with $N_d$ being equal to the number of terms in the series expansions. The resulting system of inhomogeneous linear equations is solved by matrix inversion. No iterations are required. A discussion of the calculated line admittance parameters as functions of width of conductors, thickness of the layers, and frequency is given. The interconnect capacitance and conductance per unit length results are given and compared with those obtained using full wave solutions, and good agreement have been obtained in all the cases treated

• The Journal of Korean Physical Therapy
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• v.32 no.3
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• pp.152-156
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• 2020

Purpose: The subjective visual vertical (SVV) test is used to evaluate the otolith function in the inner ear. This study compared the different balance ability according to the results of the SVV in healthy adults. Methods: This study recruited 30 normal healthy subjects who did not have neurological and musculoskeletal disorders. The subjects were divided into experimental and control groups based on the results of SVV: experimental group, >2°; control group, <2°. The static balance ability was evaluated using the Fourier Index, which could evaluate the balance capacity objectively and quantitatively. Results: The mean angle of the SVV in the experimental and control groups was 4.44° and 0.59°, respectively. In the result of the Fourier series, the F1 frequency band in the experimental group showed a significantly higher value under one condition compared to the control group (p<0.05). In the F2-4 and F5-6 frequency bands, the experimental group showed a significant increase in the Fourier series value under the four conditions compared to the control group (p<0.05). In the F7-8 frequency band, significantly higher values of the Fourier series were observed in the experimental group under the three different conditions (p<0.05). Conclusion: These results showed increased trunk sway while maintaining static balance in the experimental group who showed a larger SVV angle compared to the control group. The SVV can be applied to evaluate the vestibular system and balance ability in normal adults.

• Journal of applied mathematics & informatics
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• v.27 no.1_2
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• pp.419-426
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• 2009

In expansion of function by special basis functions, properties of expansion kernel are very important. In the Fourier series, the series are expressed by the convolution with Dirichlet kernel. We investigate some of properties of kernel in wavelet expansions both in one and higher dimensions.

• Bulletin of the Korean Mathematical Society
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• v.21 no.2
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• pp.138-138
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• 1984

• Kyungpook Mathematical Journal
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• v.14 no.1
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• pp.101-111
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• 1974