• 제목/요약/키워드: Iteration scheme

검색결과 243건 처리시간 0.025초

회전 진동하는 원형실린더 주위 유동의 폐쇄효과 연구 (BLOCKAGE EFFECT ON FLOWS AROUND A ROTATIONALLY OSCILLATING CIRCULAR CYLINDER)

  • 강승희;권오준
    • 한국전산유체공학회지
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    • 제13권4호
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    • pp.33-38
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    • 2008
  • For study on the unsteady blockage effect, flows around a rotationally oscillating circular cylinder with relatively low forcing frequency in closed test-section wind tunnels have been numerically investigated by solving compressible Navier-Stokes equations. The numerical scheme is based on a node-based finite-volume method with the Roe's flux-difference splitting and an implicit time-integration method coupled with dual time-step sub-iteration. The computed results of the oscillating cylinder in the test section showed that the fluctuations of lift and drag are augmented by the blockage effects. The drag further increases because of low base pressure. The pressure on the test section wall shows the harmonics having the oscillating and the shedding frequencies contained in the blockage effect.

TRAVELING WAVES OF AN SIRS EPIDEMIC MODEL WITH SPATIAL DIFFUSION AND TIME DELAY

  • Du, Yanke;Xu, Rui
    • Journal of applied mathematics & informatics
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    • 제30권3_4호
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    • pp.635-646
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    • 2012
  • This paper is concerned with an SIRS epidemic model with spatial diffusion and time delay representing the length of the immunity period. By using a new cross iteration scheme and Schauder's fixed point theorem, we reduce the existence of traveling wave solutions to the existence of a pair of upper-lower solutions. By constructing a newfashioned pair of upper-lower solutions, we derive the existence of a traveling wave solution connecting the uninfected steady state and the infected steady state.

Beamforming for Downlink Multiuser MIMO Time-Varying Channels Based on Generalized Eigenvector Perturbation

  • Yu, Heejung;Lee, Sok-Kyu
    • ETRI Journal
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    • 제34권6호
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    • pp.869-878
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    • 2012
  • A beam design method based on signal-to-leakage-plus-noise ratio (SLNR) has been recently proposed as an effective scheme for multiuser multiple-input multiple-output downlink channels. It is shown that its solution, which maximizes the SLNR at a transmitter, can be simply obtained by the generalized eigenvectors corresponding to the dominant generalized eigenvalues of a pair of covariance matrices of a desired signal and interference leakage plus noise. Under time-varying channels, however, generalized eigendecomposition is required at each time step to design the optimal beam, and its level of complexity is too high to implement in practical systems. To overcome this problem, a predictive beam design method updating the beams according to channel variation is proposed. To this end, the perturbed generalized eigenvectors, which can be obtained by a perturbation theory without any iteration, are used. The performance of the method in terms of SLNR is analyzed and verified using numerical results.

ANALYTICAL SOLUTION OF SINGULAR FOURTH ORDER PARABOLIC PARTIAL DIFFERENTIAL EQUATIONS OF VARIABLE COEFFICIENTS BY USING HOMOTOPY PERTURBATION TRANSFORM METHOD

  • Gupta, V.G.;Gupta, Sumit
    • Journal of applied mathematics & informatics
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    • 제31권1_2호
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    • pp.165-177
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    • 2013
  • In this paper, we apply Homotopy perturbation transform method (HPTM) for solving singular fourth order parabolic partial differential equations with variable coefficients. This method is the combination of the Laplace transform method and Homotopy perturbation method. The nonlinear terms can be easily handled by the use of He's polynomials. The aim of using the Laplace transform is to overcome the deficiency that is mainly caused by unsatisfied conditions in other semi-analytical methods such as Homotopy perturbation method (HPM), Variational iteration method (VIM) and Adomain Decomposition method (ADM). The proposed scheme finds the solutions without any discretization or restrictive assumptions and avoids the round-off errors. The comparison shows a precise agreement between the results and introduces this method as an applicable one which it needs fewer computations and is much easier and more convenient than others, so it can be widely used in engineering too.

Heat and mass transfer of a second grade magnetohydrodynamic fluid over a convectively heated stretching sheet

  • Das, Kalidas;Sharma, Ram Prakash;Sarkar, Amit
    • Journal of Computational Design and Engineering
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    • 제3권4호
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    • pp.330-336
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    • 2016
  • The present work is concerned with heat and mass transfer of an electrically conducting second grade MHD fluid past a semi-infinite stretching sheet with convective surface heat flux. The analysis accounts for thermophoresis and thermal radiation. A similarity transformations is used to reduce the governing equations into a dimensionless form. The local similarity equations are derived and solved using Nachtsheim-Swigert shooting iteration technique together with Runge-Kutta sixth order integration scheme. Results for various flow characteristics are presented through graphs and tables delineating the effect of various parameters characterizing the flow. Our analysis explores that the rate of heat transfer enhances with increasing the values of the surface convection parameter. Also the fluid velocity and temperature in the boundary layer region rise significantly for increasing the values of thermal radiation parameter.

STRONG CONVERGENCE IN NOOR-TYPE ITERATIVE SCHEMES IN CONVEX CONE METRIC SPACES

  • LEE, BYUNG-SOO
    • 한국수학교육학회지시리즈B:순수및응용수학
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    • 제22권2호
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    • pp.185-197
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    • 2015
  • The author considers a Noor-type iterative scheme to approximate com- mon fixed points of an infinite family of uniformly quasi-sup(fn)-Lipschitzian map- pings and an infinite family of gn-expansive mappings in convex cone metric spaces. His results generalize, improve and unify some corresponding results in convex met- ric spaces [1, 3, 9, 16, 18, 19] and convex cone metric spaces [8].

SAR Imaging 시스템의 신호 대역폭 추정에 따른 위상오차 제거기법 연구 (The Phase Error Correction Scheme Using the Iterative Signal Bandwidth Estimation in SAR Imaging System)

  • 김형주;최정희
    • 한국지능시스템학회:학술대회논문집
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    • 한국퍼지및지능시스템학회 2000년도 추계학술대회 학술발표 논문집
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    • pp.463-466
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    • 2000
  • SAR imaging 시스템 전파환경에서 목표물의 정보를 성공적으로 추출해 내기 위해서는 반사된 신호를 수신할 때 Coherent detection이 필수적이다. 수신시 Incoherent detection은 복소 위상오차 형태로 나타나서 실제 목표물의 영상에 심각한 Degradation을 야기시켜 치명적인 결과를 초래하게된다. 본 논문에서는 하나의 목표물에서 수신되는 신호를 파동방정식으로부터 모델링하고 모델링된 신호의 각 주파수대의 조합에 의해 전체 수신신호로부터 위상오차의 기울기를 유도한다. 더욱더 정확한 위상오차를 추정하기 위해 추정된 위상오차로부터 수신신호에 포함된 오차를 제거하고, 오차가 제거된 신호의 대역폭을 추정한다. 추정된 대역폭에 맞도록 알고리즘에 재 적용시켜 교정되지 못한 오차를 추정해 나간다. 이때 반복적인 위상오차 제거기법을 적용하고 Iteration의 종료를 자동으로 결정하기 위해 지능형 대역폭 추정 기법을 제시한다. 컴퓨터의 모의 실험에서, 위상오차를 포함한 수신 신호로부터 알고리즘을 적용하여 오차를 제거하고,, Wavefront Reconstruction 기법에 적용시켜 알고리즘의 성능을 영상으로 확인한다.

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ON THE STRONG CONVERGENCE THEOREMS FOR ASYMPTOTICALLY NONEXPANSIVE SEMIGROUPS IN BANACH SPACES

  • Chang, Shih-Sen;Zhao, Liang Cai;Wu, Ding Ping
    • Journal of applied mathematics & informatics
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    • 제27권1_2호
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    • pp.13-23
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    • 2009
  • Some strong convergence theorems of explicit iteration scheme for asymptotically nonexpansive semi-groups in Banach spaces are established. The results presented in this paper extend and improve some recent results in [T. Suzuki. On strong convergence to common fixed points of nonexpansive semigroups in Hilbert spaces, Proc. Amer. Math. Soc. 131(2002)2133-2136; H. K. Xu. A strong convergence theorem for contraction semigroups in Banach spaces, Bull. Aust. Math. Soc. 72(2005)371-379; N. Shioji and W. Takahashi. Strong convergence theorems for continuous semigroups in Banach spaces, Math. Japonica. 1(1999)57-66; T. Shimizu and W. Takahashi. Strong convergence to common fixed points of families of nonexpansive mappings, J. Math. Anal. Appl. 211(1997)71-83; N. Shioji and W. Takahashi. Strong convergence theorems for asymptotically nonexpansive mappings in Hilbert spaces, Nonlinear Anal. TMA, 34(1998)87-99; H. K. Xu. Approximations to fixed points of contraction semigroups in Hilbert space, Numer. Funct. Anal. Optim. 19(1998), 157-163.]

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주어진 고유주파수를 갖는 구조물의 위상최적설계 (Topology Design of a Structure with a Specified Eigenfrequency)

  • 이종환;민승재
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집C
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    • pp.392-397
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    • 2001
  • Topology optimization is applied to determine the layout of a structure whose eigenfrequency coincides with a specified frequency. The topology optimization problem is formulated to minimize the difference between the structural frequency and a given frequency using the homogenization method and the modified optimality criteria method. It turns out that the value of a weighting factor in the updating scheme plays an important role to achieve both a suitable speed and a stable convergence of an algorithm. Unlike a constant weighting factor in previous works, it is suggested that a weight factor is varied during the iteration to control the amount of the frequency change. To substantiate the proposed approach two-dimensional structural design problems are presented and the resulted topology layouts for the specified eigenfrequency are compared to layouts for maximizing the corresponding eigenfrequency.

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Re-Entry Trajectory Tracking Via an Inverse Dynamics Method

  • Lee, Dae-Woo;Cho, Kyeum-Rae;Hui Yan
    • Journal of Mechanical Science and Technology
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    • 제18권9호
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    • pp.1519-1528
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    • 2004
  • Atmospheric Re-Entry guidance is divided as longitudinal and lateral. This paper proposes a longitudinal reference trajectory and control law using the inverse dynamics method with pseudospectral Legendre method. Application of this method into Re-Entry problem forces a power of calculation time-reduction due to unnecessary of integration or any iteration as well as sufficient accuracy convergence. The used guidance scheme is time-to-go.