• Title/Summary/Keyword: Nonlinear array

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Flow-induced instability and nonlinear dynamics of a tube array considering the effect of a clearance gap

  • Lai, Jiang;Sun, Lei;Li, Pengzhou
    • Nuclear Engineering and Technology
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    • v.51 no.6
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    • pp.1650-1657
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    • 2019
  • Fluidelastic instability and nonlinear dynamics of tube bundles is a key issue in a steam generator. Especially, once the post-instability motion of the tube becomes larger than the clearance gap to other tubes, effective contact or impact between the tubes under consideration and the other tube inevitable. There is seldom theoretical analysis to the nonlinear dynamic characteristics of a tube array in two-phase flow. In this paper, experimental and numerical studies were utilized to obtain the critical velocity of the flow-induced instability of a rotated triangular tube array. The calculation results agreed well with the experimental data. To explore the post-instability dynamics of the tube array system, a Runge-Kutta scheme was used to solve the nonlinear governing equations of tube motion. The numerical results indicated that, when the flow pitch velocity is larger than the critical velocity, the tube array system is undergoing a limit cycle motion, and the dynamic characteristics of the tube array are almost similar for different void fractions.

Iterative Polynomial Fitting Technique Using Polynomial Coefficients for the Nonlinear Line Array Shape Estimation (비선형 선배열 형상 추정을 위한 계수 반복 다항 근사화 기법)

  • Cho, Chom Gun
    • Journal of the Korea Institute of Military Science and Technology
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    • v.9 no.2 s.25
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    • pp.20-25
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    • 2006
  • Low frequency towed line array with high array gain and beam resolution is a long range surveillance sensor for anti-submarine warfare. The beam characteristics is however deteriorated due to the distorted line array sensor caused by low towing speed, wind, current, and towing ship maneuvering. An adaptive beamforming method is utilized in this paper to enhance the distorted line array beam performance by estimating and compensating the nonlinear array shape. A polynomial curve fitting in the least square sense is used to estimate the array shape iteratively with the distributed heading sensors data along the array. Real time array shape estimation and nonlinear array beam calculation is applied to a very long towed line array sensor system and the beam performance is evaluated and compared to the linear beamformer for the simulation and sea trial data.

Effects of curvature on leverage in nonlinear regression

  • Kahng, Myung-Wook
    • Journal of the Korean Data and Information Science Society
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    • v.20 no.5
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    • pp.913-917
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    • 2009
  • The measures of leverage in linear regression has been extended to nonlinear regression models. We consider several curvature measures of nonlinearity in an estimation situation. The relationship between measures of leverage and statistical curvature are explored in nonlinear regression models. The circumstances under which the Jacobian leverage reduces to a tangent plane leverage are discussed in connection with the effective residual curvature of the nonlinear model.

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A Study on Signal Parameters Estimation via Nonlinear Minimization

  • Jeong, Jung-Sik
    • Journal of Navigation and Port Research
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    • v.28 no.4
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    • pp.305-309
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    • 2004
  • The problem for parameters estimation of the received signals impinging on array sensors has long been of great research Interest in a great variety of applications, such as radar, sonar, and land mobile communications systems. Conventional subspace-based algorithms, such as MUSIC and ESPRIT, require an extensive computation of inverse matrix and eigen-decomposition In this paper, we propose a new parameters estimation algorithm via nonlinear minimization, which is simplified computationally and estimates signal parameters simultaneously.

Development of an Educational System and Real Time Nonlinear Control (I) (교육용 시스템 개발과 실시간 비선형 제어(I))

  • 박성욱
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.51 no.12
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    • pp.562-570
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    • 2002
  • The Purpose of this paper is to design and manufacture an educational system in order to demonstrate the causes and effects of electromagnetic induction.'rho educational system described in this study is a "jumping ring apparatus". This system demonstrates the principle of electromagnetic induction, a force from AC sources, Lenz's law of repulsion and transformer. The educational system is composed of a jumping ring apparatus, a sensor array, encoder, A/D converter, D/A converter and nonlinear controller. The educational system is controlled by 586 PC using Turbo C program. The sensor array is composed of 20 optical sensors. The nonlinear controller consists of nonlinear control algorithm and control board included SCR, FET and phase controller. The A/D converter is used to show the height of ring position to analog for an education purpose. The control signal calculated from the nonlinear control of algorithm send control board through 8 bit D/A convertor. Experiment results are given to verify that Proposed nonlinear controller is useful in on line control of the educational system.al system.

MULTIPLE SOLUTIONS OF A PERTURBED YAMABE-TYPE EQUATION ON GRAPH

  • Liu, Yang
    • Journal of the Korean Mathematical Society
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    • v.59 no.5
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    • pp.911-926
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    • 2022
  • Let u be a function on a locally finite graph G = (V, E) and Ω be a bounded subset of V. Let 𝜀 > 0, p > 2 and 0 ≤ λ < λ1(Ω) be constants, where λ1(Ω) is the first eigenvalue of the discrete Laplacian, and h : V → ℝ be a function satisfying h ≥ 0 and $h{\not\equiv}0$. We consider a perturbed Yamabe equation, say $$\{\begin{array}{lll}-{\Delta}u-{\lambda}u={\mid}u{\mid}^{p-2}u+{\varepsilon}h,&&\text{ in }{\Omega},\\u=0,&&\text{ on }{\partial}{\Omega},\end{array}$$ where Ω and ∂Ω denote the interior and the boundary of Ω, respectively. Using variational methods, we prove that there exists some positive constant 𝜀0 > 0 such that for all 𝜀 ∈ (0, 𝜀0), the above equation has two distinct solutions. Moreover, we consider a more general nonlinear equation $$\{\begin{array}{lll}-{\Delta}u=f(u)+{\varepsilon}h,&&\text{ in }{\Omega},\\u=0,&&\text{ on }{\partial}{\Omega},\end{array}$$ and prove similar result for certain nonlinear term f(u).

EXISTENCE OF NONTRIVIAL SOLUTIONS OF THE NONLINEAR BIHARMONIC SYSTEM

  • Jung, Tacksun;Choi, Q.-Heung
    • Korean Journal of Mathematics
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    • v.16 no.2
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    • pp.135-143
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    • 2008
  • We investigate the existence of nontrivial solutions of the nonlinear biharmonic system with Dirichlet boundary condition $$(0.1)\;\begin{array}{lcr}{\Delta}^2{\xi}+c{\Delta}{\xi}={\mu}h({\xi}+{\eta})\;in{\Omega},\\{\Delta}^2{\eta}+c{\Delta}{\eta}={\nu}h({\xi}+{\eta})\;in{\Omega},\end{array}$$ where $c{\in}R$ and ${\Delta}^2$ denote the biharmonic operator.

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Modeling and Analysis of Solar Array of KOMPSAT (다목적 위성 태양전지 모델링 및 해석)

  • 정규범;이상욱;최완식
    • Proceedings of the KIPE Conference
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    • 1997.07a
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    • pp.365-369
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    • 1997
  • In this paper, solar array of KOMPSAT was modeled and analyzed. The modeling results of solar array was achieved by neural algorithm, which is powerful of nonlinear system with a few data sets. The algorithm was analyzed and verified by simulation considering on solar cell data of KOMPSAT. The characteristics VI curves and power generation of solar array are analyzed by using the modeling.

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Signal Parameters Estimation in Array Sensors via Nonlinear Minimization. (비선형 최소화 방법을 이용한 수신신호의 파라미터 추정알고리즘에 관한 연구)

  • Jeong, Jung-Sik;Park, Sung-Hyeon;Kim, Chul-Seung;Ahn, Young-sup
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2004.04a
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    • pp.305-309
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    • 2004
  • The problem for parameters estimation of the received signals impinging on array sensors has long been of great research interest in a great variety of applications, such as radar, sonar, and land mobile communications systems. Conventional subspace-based algorithms, such as MUSIC and ESPRIT, require an extensive computation of inverse matrix and eigen-decomposition. In this paper, we propose a new parameters estimation algorithm via nonlinear minimization, which is simplified computationally and estimates signal parameters simultaneously.

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Improvement of Control Performance of Array-Sensor System Using Soft Computing (Soft Computing을 이용한 배열 센서 시스템의 제어 성능 개선)

  • Na, Seung-You;Ahn, Myung-Kook
    • Journal of Sensor Science and Technology
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    • v.12 no.2
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    • pp.79-87
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    • 2003
  • In this paper, we propose a method to obtain a linear characteristic using soft computing for systems which have array sensors of nonlinear characteristics. Also a procedure utilizing the pattern information of array sensors without additional sensors is proposed to reduce disturbance effects. For a typical example, even a single CdS cell for CdS array has nonlinear characteristics. Overall linear characteristic for CdS array is obtained using fuzzy logic for each cell and overlapped portion. In addition, further improvement for linearization is obtained applying genetic algorithms for the parameters of membership functions. Also the effect of disturbing external light changes to the CdS array can be reduced without using any additional sensors for calibration. The proposed method based on fuzzy logic shows improvements for position measurements and disturbance reduction to external light changes due to the fuzziness of the shadow boundary as well as the inherent nonlinearity of the CdS array. This improvement is shown by applying the proposed method to the ball position measurements of a magnetic levitation system.