• Title/Summary/Keyword: fourier series

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Trend Analysis for Stratospheric Ozone Concentration in the Middle Latitude Northern Hemisphere Using HALOE Data (HALOE 자료를 이용한 중위도 지역의 오존농도 추이분석)

  • Ka, Soo-Hyun;Kwon, Mi-Ra;Oh, Jung-Jin
    • Journal of Korean Society for Atmospheric Environment
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    • v.21 no.4
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    • pp.413-422
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    • 2005
  • The ozone concentration measured by HALOE (Ver 19) from Oct. 1991 to Dec. 2003 is used for analyzing the variation of ozone concentration. The HALOE loaded in UARS is observing several gases in the atmosphere, from 10km to 80km. Fourier analysis of these data in the middle latitude northern hemisphere is reported in this paper. To detect any possible long term trends, the fourier transformed time series was back transformed after removing signals with time periods of less than 6 months. Although the results clearly show the strong annual cycle, it is difficult to show any long term trends from the fourier series. We also compared the ozone volume mixing ratio's from HALOE with that from the ground-based radiometry to evaluate the accuracy of microwave observation at Sookmyung Women's University.

DERIVATIVE FORMULAE FOR MODULAR FORMS AND THEIR PROPERTIES

  • Aygunes, Aykut Ahmet
    • Journal of the Korean Mathematical Society
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    • v.52 no.2
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    • pp.333-347
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    • 2015
  • In this paper, by using the modular forms of weight nk ($2{\leq}n{\in}\mathbb{N}$ and $k{\in}\mathbb{Z}$), we construct a formula which generates modular forms of weight 2nk+4. This formula consist of some known results in [14] and [4]. Moreover, we obtain Fourier expansion of these modular forms. We also give some properties of an operator related to the derivative formula. Finally, by using the function $j_4$, we obtain the Fourier coefficients of modular forms with weight 4.

A study on Optimizing Fourier Series Density estimates (퓨리에 급수기법에 의한 밀도함수추정의 최적화 고찰)

  • Kim, Jong-Tae;Lee, Sung-Ho;Kim, Kyung-Moo
    • Journal of the Korean Data and Information Science Society
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    • v.8 no.1
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    • pp.9-20
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    • 1997
  • Several methods are proposed for optimizing Fourier series estimators with respect to Mean Integrated Square Error metrics. Traditionally, such method have followed. one of two basic strategies; A stopping rules or the rules of determine multipliers. A central hypothesis of this study is that better estimates can be obtained by combining the two strategies. A new multiplier sequence is proposed, which used in conjunction with any of the stopping rules, is shown to improve the performance of estimator which relies solely on a stopping rule.

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A NUMERICAL METHOD OF PREDRTERMINED OPTIMAL RESOLUTION FOR A REDUNDANT MANIPULATOR

  • Won, Jong-Hwa;Choi, Byoung-Wook;Chung, Myung-Jin
    • 제어로봇시스템학회:학술대회논문집
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    • 1990.10b
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    • pp.1145-1149
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    • 1990
  • This paper proposes a numerical method for redundant manipulators using predetermined optimal resolution. In order to obtain optimal joint trajectories, it is desirable to formulate redundancy resolution as an optimization problem having an integral cost criterion. We predetermine the trajectories of redundant joints in terms of the Nth partial sum of the Fourier series, which lead to the solution in the desirable homotopy class. Then optimal coefficients of the Fourier series, which yield the optimal solution within the predetermined class, are searched by the Powell's method. The proposed method is applied to a 3-link planar manipulator for cyclic tasks in Cartesian space. As the results, we can obtain the optimal solution in the desirable homotopy class without topological liftings of the solution. To show the validity of the proposed method, we analyze both optimal and extremal solutions by the Fast Fourier Transform (FFT) and discuss joint trajectories on the phase plane.

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Natural Vibration Analysis of Two Circular Plates Coupled with Bounded Fluid (갇힌 유체로 연성된 두 원판의 고유진동 해석)

  • 정명조;정경훈
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.11 no.9
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    • pp.439-453
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    • 2001
  • This study deals with the free vibration of two identical circular plates coupled with a bounded fluid. An analytical method based on the finite Fourier-Bessel series expansion and Rayleigh-Ritz method is suggested. In the theory, it is assumed that the ideal fluid in a rigid cylindrical container and the two plates are clamped along the plate edges. The proposed method is verified by the finite element analysis using commercial program with a good accuracy. Two transverse vibration modes, namely in-phase and out-of-phase, are observed alternately in the fluid-coupled system when the number of nodal circles increases for the fixed nodal diameter. The effect of gap between the plates on the fluid-coupled natural frequencies sis also investigated.

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A 2D hybrid stress element for improved prediction of the out-of-plane fields using Fourier expansion

  • Feng, M.L.;Dhanasekar, M.;Xiao, Q.Z.
    • Structural Engineering and Mechanics
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    • v.13 no.5
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    • pp.491-504
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    • 2002
  • Recently we formulated a 2D hybrid stress element from the 3D Hellinger-Reissner principle for the analysis of thick bodies that are symmetric to the thickness direction. Polynomials have typically been used for all the displacement and stress fields. Although the element predicted the dominant stress and all displacement fields accurately, its prediction of the out-of-plane shear stresses was affected by the very high order terms used in the polynomials. This paper describes an improved formulation of the 2D element using Fourier series expansion for the out-of-plane displacement and stress fields. Numerical results illustrate that its predictions have markedly improved.

Iterative Learning Control with Feedback Using Fourier Series with Application to Robot Trajectory Tracking (퓨리에 급수 근사를 이용한 궤환을 가진 반복 학습제어와 로보트 궤적 추종에의 응용)

  • ;;Zeungnam Bien
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.30B no.4
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    • pp.67-75
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    • 1993
  • The Fourier series are employed to approximate the input/output(I/O) characteristics of a dynamic system and, based on the approximation, a new learing control algorithm is proposed in order to find iteratively the control input for tracking a desired trajectory. The use of the Fourier approximation of I/O renders at least a couple of useful consequences: the frequency characteristics of the system can be used in the controller design and the reconstruction of the system states is not required. The convergence condition of the proposed algorithm is provided and the existence and uniqueness of the desired control input is discussed. The effectiveness of the proposed algorithm is illustrated by computer simulation for a robot trajectory tracking. It is shown that, by adding feedback term in learning control algorithm, robustness and convergence speed can be improved.

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Analysis of the Three Phase Inductor-Converter Bridge Circuit by Means of State-Space Averaging Method. (상태변수 평균화법에 의한 삼상 ICB회로 해석)

  • Park, Min-Ho;Hong, Soon-Chan;Choy, Ick;Oh, Soo-Hong
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.38 no.9
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    • pp.701-709
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    • 1989
  • The time-averaged behavior of the three-phase Inductor-Converter Bridge (ICB) circuit has been analyzed by using the state-space averaging method. Especially, a second order approximation in the matrix expansion makes the analysis possible. The results are in a closed form which is quite different from the conventional solution obtained by using the Fourier Series. Therefore, the computational difficulties in evaluating the infinite Fourier series can be avoided and the results derived in this paper are available expecially in real time control. By comparing with the Fourier result, it has been verified that the analysis by means of the state-space averaging method is more accurate and simple. The digital simulation and the equivalent experiments have also been carried out to confirm the theoretical results.

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Space Harmonic Field by Interaction of Stator and Rotor Slots (고정자 슬롯과 회전자 슬롯의 상호작용에 의한 공간 고조파)

  • Lee, Eun-Woong;Cho, Hyun-Gil;Kim, Jong-Gyeum;Jeong, Jong-Ho;Kim, Il-Jung
    • Proceedings of the KIEE Conference
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    • 1995.07a
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    • pp.42-45
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    • 1995
  • This paper describes the flux density in air gap, harmonic torques occurring by inadequate slot combination of induction motor using the fourier series. The analysis uses DFT(Discrete Fourier transform) to analyze harmonic orders of flux density. It is certified that the harmonic flux density has the same result using Fourier series and FEM.

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A Study on the Characteristics of Thyristor Controlled Shunt Compensator (싸이리스터제어 병렬보상기의 특성 연구)

  • 정교범
    • The Transactions of the Korean Institute of Power Electronics
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    • v.4 no.4
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    • pp.368-376
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    • 1999
  • This paper studies the operational characteristics of thyristor controlled shunt compensator in a simple power t transmission system. With Fourier series representation of the thyristor switching action and the system parameters, t the thyristor current equations are derived, which transmit the required real power of the simple power transmission s system. Bisection algorithm is used to solve the thyristor current equations, which informs the thyristor firing an밍e, t the thyristor conduction an밍e, the power flows and the harmonic characteristics. The stability analysis is performed w with the theory of Poincare mapping for the nonlinear discrete periodic dynamic system. EMTP simulations at the v various operating points show the transient characteristics of the thyristor controlled shunt compensator and C correspond to the results calculated with Fourier series representation and the stability analysis.

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