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Articoli di riviste sul tema "Nonlinear"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 7 settembre 2024

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1

TRUEBA, JOSÉ L., JOAQUÍN RAMS e MIGUEL A. F. SANJUÁN. "ANALYTICAL ESTIMATES OF THE EFFECT OF NONLINEAR DAMPING IN SOME NONLINEAR OSCILLATORS". International Journal of Bifurcation and Chaos 10, n. 09 (settembre 2000): 2257–67. http://dx.doi.org/10.1142/s0218127400001419.

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This paper reports on the effect of nonlinear damping on certain nonlinear oscillators, where analytical estimates provided by the Melnikov theory are obtained. We assume general nonlinear damping terms proportional to the power of velocity. General and useful expressions for the nonlinearly damped Duffing oscillator and for the nonlinearly damped simple pendulum are computed. They provide the critical parameters in terms of the damping coefficient and damping exponent, that is, the power of the velocity, for which complicated behavior is expected. We also consider generalized nonlinear damped systems, which may contain several nonlinear damping terms. Using the idea of Melnikov equivalence, we show that the effect of nonlinear dissipation can be equivalent to a linearly damped nonlinear oscillator with a modified damping coefficient.

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2

Wang, Yunze, Yan Sheng, Shan Liu, Ruwei Zhao, Tianxiang Xu, Tiefeng Xu, Feng Chen e Wieslaw Krolikowski. "Wavelength-dependent nonlinear wavefront shaping in 3D nonlinear photonic crystal". Chinese Optics Letters 22, n. 7 (2024): 071901. http://dx.doi.org/10.3788/col202422.071901.

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3

Kosek, Zdeněk. "Nonlinear boundary value problem for a system of nonlinear ordinary differential equations". Časopis pro pěstování matematiky 110, n. 2 (1985): 130–44. http://dx.doi.org/10.21136/cpm.1985.108595.

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4

Tejedor Sastre, María Teresa, e Christian Vanhille. "Nonlinear Maximization of the Sum-Frequency Component from Two Ultrasonic Signals in a Bubbly Liquid". Sensors 20, n. 1 (23 dicembre 2019): 113. http://dx.doi.org/10.3390/s20010113.

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Techniques based on ultrasound in nondestructive testing and medical imaging analyze the response of the source frequencies (linear theory) or the second-order frequencies such as higher harmonics, difference and sum frequencies (nonlinear theory). The low attenuation and high directivity of the difference-frequency component generated nonlinearly by parametric arrays are useful. Higher harmonics created directly from a single-frequency source and the sum-frequency component generated nonlinearly by parametric arrays are attractive because of their high spatial resolution and accuracy. The nonlinear response of bubbly liquids can be strong even at relatively low acoustic pressure amplitudes. Thus, these nonlinear frequencies can be generated easily in these media. Since the experimental study of such nonlinear waves in stable bubbly liquids is a very difficult task, in this work we use a numerical model developed previously to describe the nonlinear propagation of ultrasound interacting with nonlinearly oscillating bubbles in a liquid. This numerical model solves a differential system coupling a Rayleigh–Plesset equation and the wave equation. This paper performs an analysis of the generation of the sum-frequency component by nonlinear mixing of two signals of lower frequencies. It shows that the amplitude of this component can be maximized by taking into account the nonlinear resonance of the system. This effect is due to the softening of the medium when pressure amplitudes rise.

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Vatanshenas, Ali. "Nonlinear Analysis of Reinforced Concrete Shear Walls Using Nonlinear Layered Shell Approach". Nordic Concrete Research 65, n. 2 (1 dicembre 2021): 63–79. http://dx.doi.org/10.2478/ncr-2021-0014.

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Abstract This study discusses nonlinear modelling of a reinforced concrete wall utilizing the nonlinear layered shell approach. Rebar, unconfined and confined concrete behaviours are defined nonlinearly using proposed analytical models in the literature. Then, finite element model is validated using experimental results. It is shown that the nonlinear layered shell approach is capable of estimating wall response (i.e., stiffness, ultimate strength, and cracking pattern) with adequate accuracy and low computational effort. Modal analysis is conducted to evaluate the inherent characteristics of the wall to choose a logical loading pattern for the nonlinear static analysis. Moreover, pushover analysis’ outputs are interpreted comprehensibly from cracking of the concrete until reaching the rupture step by step.

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6

Kubáček, Lubomír. "Nonlinear error propagation law". Applications of Mathematics 41, n. 5 (1996): 329–45. http://dx.doi.org/10.21136/am.1996.134330.

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7

Knobloch, H. W. "Observability of nonlinear systems". Mathematica Bohemica 131, n. 4 (2006): 411–18. http://dx.doi.org/10.21136/mb.2006.133974.

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8

Gerasimchuk, V. S., I. V. Gerasimchuk e N. I. Dranik. "Solutions of Nonlinear Schrodinger Equation with Two Potential Wells in Linear / Nonlinear Media". Zurnal matematiceskoj fiziki, analiza, geometrii 12, n. 2 (25 giugno 2016): 168–76. http://dx.doi.org/10.15407/mag12.02.168.

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9

Wang, Meiqiao, e Wuquan Li. "Distributed adaptive control for nonlinear multi-agent systems with nonlinear parametric uncertainties". Mathematical Biosciences and Engineering 20, n. 7 (2023): 12908–22. http://dx.doi.org/10.3934/mbe.2023576.

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<abstract><p>This paper considers the distributed tracking control problem for a class of nonlinear multi-agent systems with nonlinearly parameterized control coefficients and inherent nonlinearities. The essential of multi-agent systems makes it difficult to directly generalize the existing works for single nonlinearly parameterized systems with uncontrollable unstable linearization to the case in this paper. To dominate the inherent nonlinearities and nonlinear parametric uncertainties, a powerful distributed adaptive tracking control is presented by combing the algebra graph theory with the distributed backstepping method, which guarantees that all the closed-loop system signals are global bounded while the range of the tracking error between the follower's output and the leader's output can be tuned arbitrarily small. Finally, a numerical example is provided to verify the validity of the developed methods.</p></abstract>

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10

Zhu, Yun-Peng, Z. Q. Lang e Yu-Zhu Guo. "Nonlinear model standardization for the analysis and design of nonlinear systems with multiple equilibria". Nonlinear Dynamics 104, n. 3 (22 aprile 2021): 2553–71. http://dx.doi.org/10.1007/s11071-021-06429-9.

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AbstractIn engineering practice, a nonlinear system stable about several equilibria is often studied by linearizing the system over a small range of operation around each of these equilibria, and allowing the study of the system using linear system methods. Theoretically, for operations beyond a small range but still within the stable regime of an equilibrium, the system behaves nonlinearly, and can be described and investigated using the Volterra series approach. However, there is still no available approach that can systematically transform the model of a nonlinear system into a form that can be studied over the whole stable regime about an equilibrium so as to facilitate the system study using the Volterra series approach. This transformation is, in the present study, referred to as nonlinear model standardization, which is the extension of the well-known concept of linearization to the nonlinear case. In this paper, a novel approach to nonlinear model standardization is proposed for nonlinear systems that can be described by a Nonlinear AutoRegressive model with eXogeneous input (NARX) or a nonlinear differential equation (NDE) model. The proposed approach is then used in three case studies covering the applications in nonlinear system analysis, nonlinear system design, and nonlinearity compensation, respectively, demonstrating the significance of the proposed nonlinear model standardization in a wide range of engineering practices.

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11

Schaefer, S., E. Vouga e R. Goldman. "Nonlinear subdivision through nonlinear averaging". Computer Aided Geometric Design 25, n. 3 (marzo 2008): 162–80. http://dx.doi.org/10.1016/j.cagd.2007.07.003.

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12

Smirnov, V. V., M. A. Kovaleva e L. I. Manevitch. "Nonlinear Dynamics of Torsion Lattices". Nelineinaya Dinamika 14, n. 2 (2018): 179–93. http://dx.doi.org/10.20537/nd180203.

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13

Moulard, Thomas, Benjamin Chr^|^eacute;tien e Eiichi Yoshida. "Software Tools for Nonlinear Optimization". Journal of the Robotics Society of Japan 32, n. 6 (2014): 536–41. http://dx.doi.org/10.7210/jrsj.32.536.

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14

Zeng, Jing, Sen Wang, Ruwei Zhao, Yongxing Liu, Tiefeng Xu, Yan Sheng e Tianxiang Xu. "Nonlinear photonic quasi-periodic spiral". Chinese Optics Letters 22, n. 3 (2024): 031902. http://dx.doi.org/10.3788/col202422.031902.

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15

Gluskin, Emanuel. "A nonlinear resistor and nonlinear inductor using a nonlinear capacitor". Journal of the Franklin Institute 336, n. 7 (settembre 1999): 1035–47. http://dx.doi.org/10.1016/s0016-0032(99)00029-0.

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16

Güttel, Stefan, e Françoise Tisseur. "The nonlinear eigenvalue problem". Acta Numerica 26 (1 maggio 2017): 1–94. http://dx.doi.org/10.1017/s0962492917000034.

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Nonlinear eigenvalue problems arise in a variety of science and engineering applications, and in the past ten years there have been numerous breakthroughs in the development of numerical methods. This article surveys nonlinear eigenvalue problems associated with matrix-valued functions which depend nonlinearly on a single scalar parameter, with a particular emphasis on their mathematical properties and available numerical solution techniques. Solvers based on Newton’s method, contour integration and sampling via rational interpolation are reviewed. Problems of selecting the appropriate parameters for each of the solver classes are discussed and illustrated with numerical examples. This survey also contains numerous MATLAB code snippets that can be used for interactive exploration of the discussed methods.

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17

Yim, S. C. S., e S. Narayanan. "Modeling and Identification of a Nonlinear SDOF Moored Structure, Part 2—Comparisons and Sensitivity Study". Journal of Offshore Mechanics and Arctic Engineering 126, n. 2 (1 maggio 2004): 183–90. http://dx.doi.org/10.1115/1.1710874.

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A system-identification technique based on the Reverse Multiple-Input/Single-Output (R-MI/SO) procedure is applied to identify the parameters of an experimental mooring system exhibiting nonlinear behavior. In Part 1, two nonlinear small-body hydrodynamic Morison type formulations: (A) with a relative-velocity (RV) model, and (B) with an independent-flow-field (IFF) model, are formulated. Their associated nonlinear system-identification algorithms based on the R-MI/SO system-identification technique: (A.1) nonlinear-structure linearly damped, and (A.2) nonlinear-structure coupled hydrodynamically damped for the RV model, and (B.1) nonlinear-structure nonlinearly damped for the IFF model, are developed for an experimental submerged-sphere nonlinear mooring system under ocean waves. The analytic models and the associated algorithms for parametric identification are described. In this companion paper (Part 2), we use the experimentally measured input wave and output system response data and apply the algorithms derived based on the multiple-input/single-output linear analysis of the reverse dynamic systems to identify the system parameters. The two nonlinear models are examined in detail and the most suitable physical representative model is selected for the mooring system considered. A sensitive analysis is conducted to investigate the coupled hydrodynamic forces modeled by the Morison equation, the nonlinear stiffness from mooring lines and the nonlinear response. The appropriateness of each model is discussed in detail.

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18

Liu, Lijun. "A simple nonlinearH∞control design method: Polynomial nonlinear control". International Journal of Robust and Nonlinear Control 28, n. 17 (12 settembre 2018): 5406–23. http://dx.doi.org/10.1002/rnc.4322.

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19

Song, Jiecheng, e Merry Ma. "Climate Change: Linear and Nonlinear Causality Analysis". Stats 6, n. 2 (15 maggio 2023): 626–42. http://dx.doi.org/10.3390/stats6020040.

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The goal of this study is to detect linear and nonlinear causal pathways toward climate change as measured by changes in global mean surface temperature and global mean sea level over time using a data-based approach in contrast to the traditional physics-based models. Monthly data on potential climate change causal factors, including greenhouse gas concentrations, sunspot numbers, humidity, ice sheets mass, and sea ice coverage, from January 2003 to December 2021, have been utilized in the analysis. We first applied the vector autoregressive model (VAR) and Granger causality test to gauge the linear Granger causal relationships among climate factors. We then adopted the vector error correction model (VECM) as well as the autoregressive distributed lag model (ARDL) to quantify the linear long-run equilibrium and the linear short-term dynamics. Cointegration analysis has also been adopted to examine the dual directional Granger causalities. Furthermore, in this work, we have presented a novel pipeline based on the artificial neural network (ANN) and the VAR and ARDL models to detect nonlinear causal relationships embedded in the data. The results in this study indicate that the global sea level rise is affected by changes in ice sheet mass (both linearly and nonlinearly), global mean temperature (nonlinearly), and the extent of sea ice coverage (nonlinearly and weakly); whereas the global mean temperature is affected by the global surface mean specific humidity (both linearly and nonlinearly), greenhouse gas concentration as measured by the global warming potential (both linearly and nonlinearly) and the sunspot number (only nonlinearly and weakly). Furthermore, the nonlinear neural network models tend to fit the data closer than the linear models as expected due to the increased parameter dimension of the neural network models. Given that the information criteria are not generally applicable to the comparison of neural network models and statistical time series models, our next step is to examine the robustness and compare the forecast accuracy of these two models using the soon-available 2022 monthly data.

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20

Kotzev, Miroslav, Xiaotang Bi, Matthias Kreitlow e Frank Gronwald. "Equivalent circuit simulation of HPEM-induced transient responses at nonlinear loads". Advances in Radio Science 15 (21 settembre 2017): 175–80. http://dx.doi.org/10.5194/ars-15-175-2017.

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Abstract. In this paper the equivalent circuit modeling of a nonlinearly loaded loop antenna and its transient responses to HPEM field excitations are investigated. For the circuit modeling the general strategy to characterize the nonlinearly loaded antenna by a linear and a nonlinear circuit part is pursued. The linear circuit part can be determined by standard methods of antenna theory and numerical field computation. The modeling of the nonlinear circuit part requires realistic circuit models of the nonlinear loads that are given by Schottky diodes. Combining both parts, appropriate circuit models are obtained and analyzed by means of a standard SPICE circuit simulator. It is the main result that in this way full-wave simulation results can be reproduced. Furthermore it is clearly seen that the equivalent circuit modeling offers considerable advantages with respect to computation speed and also leads to improved physical insights regarding the coupling between HPEM field excitation and nonlinearly loaded loop antenna.

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21

PENG, SHIGE. "NONLINEAR EXPECTATIONS AND NONLINEAR MARKOV CHAINS". Chinese Annals of Mathematics 26, n. 02 (aprile 2005): 159–84. http://dx.doi.org/10.1142/s0252959905000154.

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22

de los Santos-Sánchez, O., e J. Récamier. "Nonlinear coherent states for nonlinear systems". Journal of Physics A: Mathematical and Theoretical 44, n. 14 (11 marzo 2011): 145307. http://dx.doi.org/10.1088/1751-8113/44/14/145307.

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23

Gao, Lei, Jia-Jun Wang e Zhen-Ya Li. "Nonlinear Susceptibility of Strongly Nonlinear composites". Communications in Theoretical Physics 27, n. 4 (15 giugno 1997): 403–6. http://dx.doi.org/10.1088/0253-6102/27/4/403.

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24

Dower, Peter M., Huan Zhang e Christopher M. Kellett. "Nonlinear -gain verification for nonlinear systems". Systems & Control Letters 61, n. 4 (aprile 2012): 563–72. http://dx.doi.org/10.1016/j.sysconle.2012.02.006.

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25

Kalaycıoğlu, Taner, e H. Nevzat Özgüven. "Nonlinear structural modification and nonlinear coupling". Mechanical Systems and Signal Processing 46, n. 2 (giugno 2014): 289–306. http://dx.doi.org/10.1016/j.ymssp.2014.01.016.

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26

Lin, Yanping, e Hong-Ming Yin. "Nonlinear parabolic equations with nonlinear functionals". Journal of Mathematical Analysis and Applications 168, n. 1 (luglio 1992): 28–41. http://dx.doi.org/10.1016/0022-247x(92)90187-i.

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27

Anguita, J. A., e M. A. Neifeld. "Nonlinear Codes for Dispersive Nonlinear Fibers". IEEE Photonics Technology Letters 16, n. 12 (dicembre 2004): 2622–24. http://dx.doi.org/10.1109/lpt.2004.836754.

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28

FAINBERG, B. D., B. ZOLOTOV e D. HUPPERT. "NONLINEAR LASER SPECTROSCOPY OF NONLINEAR SOLVATION". Journal of Nonlinear Optical Physics & Materials 05, n. 04 (ottobre 1996): 789–807. http://dx.doi.org/10.1142/s0218863596000568.

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In this study we show that the transient four-photon spectroscopy with pulses longer than the electronic transition dephasing can be used for nonlinear solvation study, i.e., when the linear response for the solvation dynamics breaks down. We have obtained new formulae describing the time evolution of the moments of the nonlinear optical spectra and, in particular, the time resolved fluorescence in the case of nonlinear solvation.

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29

Abdel-Rohman, Mohamed, e Hasan Al-Sanad. "Control of Nonlinear Vibrations of Foundations Built in Sandy Soil". Journal of Vibration and Control 2, n. 1 (gennaio 1996): 53–68. http://dx.doi.org/10.1177/107754639600200104.

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Sandy soils behave nonlinearly at stress levels below the peak stress. This influences the dynamic response of the foundations built on sandy soil. This paper shows first the nonlinear vibration response of a block-type foundation due to the vertical, horizontal, and rocking excitations. The nonlinear vibration responses are compared with the linear response assuming linear soil behavior. The second part of the paper shows how to control the harmful effects due to the nonlinear vibrations using passive and active control mechanisms attached to the foundation.

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30

Semenikhina, Diana V., e Nikolay N. Gorbatenko. "Nonlinear Cylindrical Markers Using Metamaterials". Remote Sensing 13, n. 24 (9 dicembre 2021): 5006. http://dx.doi.org/10.3390/rs13245006.

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In this paper, the research of nonlinear cylindrical metastructure was obtained. An algorithm for finding the total field of a nonlinearly loaded perfectly conducting cylinder covered with a metamaterial (MM) layer based on Maxwell’s equations with nonlinear boundary conditions on the surface of nonlinear loads (NL) was developed. A software package implementing this algorithm was created. Based on the results of numerical calculations of the program, the scattering diagrams of a metal cylinder with NL, covered with a layer of MM at the fundamental, second, and third harmonics were obtained. The dependences of the harmonics of the scattered field on the parameters of nonlinear loads were also studied. With the help of numerical simulation using Ansys HFSS, the extract procedure of the effective parameters of cylindrical MM was realized. Based on the results of calculation and numerical simulation, a model of a nonlinear cylindrical structure of two radii was made and an experimental study was carried out. As a result of the experiment, the frequency characteristics of the metastructure were obtained at various angles of incidence of the wave. The results of numerical simulation were confirmed by the results of the experiment. It is shown that the use of the provided nonlinear cylindrical marker with metamaterial makes it possible to obtain the levels of the first and second harmonics in a scattered field of the same order. This structure can be used as a nonlinear marker in both military and civilian areas.

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Park, Dong-Hun, e Seung-O. Park. "Nonlinear Stability Analysis of Boundary Layers by using Nonlinear Parabolized Stabiltiy Equations". Journal of the Korean Society for Aeronautical & Space Sciences 39, n. 9 (1 settembre 2011): 805–15. http://dx.doi.org/10.5139/jksas.2011.39.9.805.

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Peng, Jiehua, Jiashi Tang e Zili Chen. "Parameter Identification of Weakly Nonlinear Vibration System in Frequency Domain". Shock and Vibration 11, n. 5-6 (2004): 685–92. http://dx.doi.org/10.1155/2004/634785.

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A new method of identifying parameters of nonlinearly vibrating system in frequency domain is presented in this paper. The problems of parameter identification of the nonlinear dynamic system with nonlinear elastic force or nonlinear damping force are discussed. In the method, the mathematic model of parameter identification is frequency response function. Firstly, by means of perturbation method the frequency response function of weakly nonlinear vibration system is derived. Next, a parameter transformation is made and the frequency response function becomes a linear function of the new parameters. Then, based on this function and with the least square method, physical parameters of the system are identified. Finally, the applicability of the proposed technique is confirmed by numerical simulation.

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Liu, Xiaofang, e Guodong Sun. "Nonlinear character analysis for bistability in virus–immune dynamics". Future Virology 14, n. 10 (ottobre 2019): 655–62. http://dx.doi.org/10.2217/fvl-2019-0059.

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Structured abstract Aim: The nonlinear characters of two linearly stable equilibrium states (virus and immune) for a theoretical virus-immune model are analyzed. Methods: Conditional nonlinear optimal perturbation (CNOP), Lyapunov method and linear singular vector method. Results & conclusion: Two linearly stable equilibrium states (immune-free and immune) with linear methods are nonlinearly unstable using the CNOP method. When the CNOP-type of initial perturbation is used in the model, the immune-free (immune) equilibrium state will be made into the immune (immune-free) equilibrium state. Through computing the variations of nonlinear terms of the model, the nonlinear effect of immune proliferation plays an important role in abrupt changes of the immune-free equilibrium state compared with the linear term. For the immune equilibrium state, the nonlinear effect of viral replication is also an important factor.

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Jafari, Mohammad, Mahmut Reyhanoglu e Zhandos Kozhabek. "Simple Learning-Based Robust Nonlinear Control of an Electric Pump for Liquid-Propellant Rocket Engines". Electronics 12, n. 16 (21 agosto 2023): 3527. http://dx.doi.org/10.3390/electronics12163527.

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This paper presents a robust nonlinear control strategy for an electric pump for liquid-propellant rocket engines. In order to compensate for model uncertainties and disturbances, a gradient-descent-based simple learning control strategy is employed that minimizes the cost function defined on the error dynamics of the nonlinear system. Detailed stability analysis for the nonlinear system is provided. Computer simulation results are included to demonstrate the effectiveness of the nonlinear control method using an electric pump model consisting of a brushless permanent-magnet direct current (DC) motor and a centrifugal pump. In particular, it is shown that by employing the developed nonlinear controller, the mass flow rate can be successfully kept at a certain level, can be changed instantly from one level to another (immediate decrease or increase), or can be changed linearly/nonlinearly, gradually, and continually for a certain period.

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Christov, Ivan C., Tyler Kress e Avadh Saxena. "Peakompactons: Peaked compact nonlinear waves". International Journal of Modern Physics B 31, n. 10 (20 aprile 2017): 1742008. http://dx.doi.org/10.1142/s0217979217420085.

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This paper is meant as an accessible introduction to/tutorial on the analytical construction and numerical simulation of a class of nonstandard solitary waves termed peakompactons. These peaked compactly supported waves arise as solutions to nonlinear evolution equations from a hierarchy of nonlinearly dispersive Korteweg–de Vries-type models. Peakompactons, like the now-well-known compactons and unlike the soliton solutions of the Korteweg–de Vries equation, have finite support, i.e., they are of finite wavelength. However, unlike compactons, peakompactons are also peaked, i.e., a higher spatial derivative suffers a jump discontinuity at the wave’s crest. Here, we construct such solutions exactly by reducing the governing partial differential equation to a nonlinear ordinary differential equation and employing a phase-plane analysis. A simple, but reliable, finite-difference scheme is also designed and tested for the simulation of collisions of peakompactons. In addition to the peakompacton class of solutions, the general physical features of the so-called [Formula: see text] hierarchy of nonlinearly dispersive Korteweg–de Vries-type models are discussed as well.

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NUGROHO, MOCHAMAD ARI BAGUS, NOVIE AYUB WINDARKO e BAMBANG SUMANTRI. "Perancangan Kendali Multilevel Inverter Satu Fasa Tiga Tingkat dengan PI+feedforward pada Beban Nonlinier". ELKOMIKA: Jurnal Teknik Energi Elektrik, Teknik Telekomunikasi, & Teknik Elektronika 7, n. 3 (30 settembre 2019): 493. http://dx.doi.org/10.26760/elkomika.v7i3.493.

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ABSTRAKSebuah konverter daya multilevel inverter diharapkan mampu untuk menyuplai tegangan AC ideal pada kondisi beban linier maupun nonlinier. Diharapkan metode kendali mampu cepat tanggap dan mampu mempertahankan bentuk tegangan AC keluaran inverter. Pengendali PI+feedforward diajukan dalam makalah ini. Pengendali ini akan diuji dengan beban linier maupun nonlinier. Beban nonlinier berupa rangkaian penyearah dengan filter kapasitor. Berdasarkan pengujian simulasi didapatkan bahwa pengendali PI+feedforward lebih cepat tanggap terhadap gangguan yang dibuktikan dengan nilai kesalahan rata-rata absolut sekitar 73% lebih kecil dari pengendali PI. Hasil Simulasi menunjukkan bahwa multilevel inverter dengan kendali PI menghasilkan THDv sebesar 0,669% pada beban linier dan sebesar 1,263% pada kondisi beban nonlinier. Sedangkan dengan kendali PI+feedforward menghasilkan THDv sebesar 0,292% pada beban linier dan sebesar 1,044% pada kondisi beban nonlinier.Kata kunci: mutilevel inverter, pengendali PI, feedforward, beban non-linier ABSTRACTA multilevel inverter power converter is expected to be able to supply ideal AC voltage in linear and nonlinear load conditions. It is expected that the control method is be able to respond quickly and be able to maintain the waveform of the inverter output AC voltage. PI + feedforward controller is proposed in this paper. This controller will be tested with linear and nonlinear loads. Nonlinear load is a rectifier circuit with a filter capacitor. Based on simulation it was found that PI + feedforward controllers were more responsive to interference as evidenced by the mean absolute error (MAE) value of about 73% less than the PI controller. Simulation results show that multilevel inverter with PI control produces THDv of 0.669% in linear load and 1.263% in nonlinear load conditions. Whereas with PI + feedforward control produces THDv of 0.292% in linear loads and of 1.044% in nonlinear load conditions.Keywords: multilevel inverter, PI controller, feedforward, non-linear load

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Narayanan, S., e S. C. S. Yim. "Modeling and Identification of a Nonlinear SDOF Moored Structure, Part 1—Hydrodynamic Models and Algorithms". Journal of Offshore Mechanics and Arctic Engineering 126, n. 2 (1 maggio 2004): 175–82. http://dx.doi.org/10.1115/1.1710875.

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The highly nonlinear responses of compliant ocean structures characterized by a large-geometry restoring force and coupled fluid-structure interaction excitation are of great interest to ocean and coastal engineers. Practical modeling, parameter identification, and incorporation of the inherent nonlinear dynamics in the design of these systems are essential and challenging. The general approach of a nonlinear system technique using very simple models has been presented in the literature by Bendat. In Part 1 of this two-part study, two specific nonlinear small-body hydrodynamic Morison type formulations: (A) with a relative-velocity (RV) model, and (B) with an independent flow-field (IFF) model, are formulated. Their associated nonlinear system-identification algorithms based on the reverse multiple-input/single-output (R-MI/SO) system-identification technique: (A.1) nonlinear-structure linearly damped, and (A.2) nonlinear-structure coupled hydrodynamically damped for the RV model, and (B.1) nonlinear-structure nonlinearly damped for the IFF model, are developed for a specific experimental submerged-sphere mooring system under ocean waves exhibiting such highly nonlinear response behaviors. In Part 2, using the measured input wave and output system response data, the algorithms derived based on the MI/SO linear analysis of the reverse dynamic systems are applied to identify the properties of the highly nonlinear system. Practical issues on the application of the R-MI/SO technique based on limited available experimental data are addressed.

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Umran, Fadhil A. "Experimental observation of the far field diffraction patterns of functionalization single and multi-walled carbon nanotubes using nonlinear diffraction technique". Iraqi Journal of Physics (IJP) 17, n. 40 (3 marzo 2019): 33–41. http://dx.doi.org/10.30723/ijp.v17i40.402.

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Nonlinear diffraction pattern can be induced by focusing CWlaser into a thin quartzes cuvette containing nanofluid. The numberof revealed pattern rings indicates to the nonlinear behavior of fluid.Here, the nonlinear refractive index of each of functionalized singlewall carbon nanotube (F-SWCNTs) suspention and multi wall carbonnanotube (F-MWCNTs) suspention have been investigatedexperimentally .Each of CNTs suspention was at volume fraction of13×10−5 and 6×10−5. Moreover the laser source at wavelength of473 nm was used. The results show that SWCNTs suspentionpossesses higher nonlinearty than other at the same volume fraction

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39

Ibrahim, E. A., e S. P. Lin. "Weakly Nonlinear Instability of a Liquid Jet in a Viscous Gas". Journal of Applied Mechanics 59, n. 2S (1 giugno 1992): S291—S296. http://dx.doi.org/10.1115/1.2899503.

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The weakly nonlinear instability of a viscous liquid jet emanated into a viscous gas contained in a coaxial vertical circular pipe is investigated as an initial-value problem. The linear stability theory predicted that the jet may become unstable either due to capillary pinching or due to interfacial stress fluctuation. The results of nonlinear stability analysis shows no tendency of supercritical stability for both of the linearly unstable modes. In fact, the nonlinear growth rate of the disturbance is faster than the exponential growth rate of the linear normal mode disturbance for the same flow parameters. Moreover, the most amplified linear normal mode disturbance evolves nonlinearly into a nonsinusoidal wave of shorter wavelength. No nonlinear instability is found for the linearly stable disturbances. Thus, while the linear theory is adequate for the prediction of the onset of jet breakup, nonlinear theory is required to describe the outcome of the jet breakup.

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40

Kahng, Myung-Wook. "Modified Studentized Residual in Nonlinear Regression". Korean Data Analysis Society 19, n. 6 (31 dicembre 2017): 2863–69. http://dx.doi.org/10.37727/jkdas.2017.19.6.2863.

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41

Potocký, Rastislav, e Van Ban To. "Confidence regions in nonlinear regression models". Applications of Mathematics 37, n. 1 (1992): 29–39. http://dx.doi.org/10.21136/am.1992.104489.

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42

Nadtoka, Oksana. "Nonlinear Optical Effects in Polymeric Azoesters". Chemistry & Chemical Technology 4, n. 3 (15 settembre 2010): 185–90. http://dx.doi.org/10.23939/chcht04.03.185.

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Abstract (sommario):

The new photochromic polymers based on methacrylic azoesters were synthesized. The azobenzene side chains of obtained polymers contain different groups of both acceptor and donor nature as well as flexible alkyl spacer. The third order nonlinear optical susceptibilities (3) of the studied solutions were measured by degenerating four wave mixing (DFWM) method. As a result, the enhancement of the molecular conjugation and the high NLO chromophore concentration in the molecular chain contribute much to heightening the third-order NLO effect. The electronic effect of the substituent on the azobenzol group and the push–pull electronic structure contributes much to enhancing the NLO property

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43

Momynov, S. B., E. S. Mukhametkarimov, I. R. Gabitov e A. E. Davletov. "Nonlinear wave interactions in modern photonics". Physical Sciences and Technology 2, n. 1 (2015): 30–36. http://dx.doi.org/10.26577/2409-6121-2015-2-1-30-36.

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44

Coarita, Ever, e Leonardo Flores. "Nonlinear Analysis of Structures Cable - Truss". International Journal of Engineering and Technology 7, n. 3 (giugno 2015): 160–69. http://dx.doi.org/10.7763/ijet.2015.v7.786.

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45

Fardad, Shima, Eric Schweisberger e Alessandro Salandrino. "Parametric resonances in nonlinear plasmonics [Invited]". Chinese Optics Letters 17, n. 12 (2019): 122402. http://dx.doi.org/10.3788/col201917.122402.

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46

Wang, Jinbo, Michael A. Spall, Glenn R. Flierl e Paola Malanotte-Rizzoli. "Nonlinear Radiating Instability of a Barotropic Eastern Boundary Current". Journal of Physical Oceanography 43, n. 7 (1 luglio 2013): 1439–52. http://dx.doi.org/10.1175/jpo-d-12-0174.1.

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Abstract (sommario):

Abstract Linear and nonlinear radiating instabilities of an eastern boundary current are studied using a barotropic quasigeostrophic model in an idealized meridional channel. The eastern boundary current is meridionally uniform and produces unstable modes in which long waves are most able to radiate. These long radiating modes are easily suppressed by friction because of their small growth rates. However, the long radiating modes can overcome friction by nonlinear energy input transferred from the more unstable trapped mode and play an important role in the energy budget of the boundary current system. The nonlinearly powered long radiating modes take away part of the perturbation energy from the instability origin to the ocean interior. The radiated instabilities can generate zonal striations in the ocean interior that are comparable to features observed in the ocean. Subharmonic instability is identified to be responsible for the nonlinear resonance between the radiating and trapped modes, but more general nonlinear triad interactions are expected to apply in a highly nonlinear environment.

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47

Wineman, Alan. "Dimensional changes during shear without normal tractions (the Poynting effect) in nonlinear viscoelastic fiber-reinforced solids". Mathematics and Mechanics of Solids 25, n. 3 (17 novembre 2019): 582–96. http://dx.doi.org/10.1177/1081286519885162.

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Abstract (sommario):

When a rectangular block of a nonlinear material is subjected to a simple shearing deformation, specific normal tractions are required to ensure that the distances between the faces of the block, i.e. its dimensions, do not change. This work investigates the time-dependent dimensional changes during shear in the absence of these normal tractions (the Poynting effect) that occur in a block composed of an incompressible nonlinearly viscoelastic fiber-reinforced solid. The material is modeled using the Pipkin–Rogers nonlinear single integral constitutive equation for viscoelasticity. This constitutive equation is used because (1) it exhibits the essential features of nonlinear viscoelasticity; (2) it is straightforward to include the material symmetry restrictions due to the reinforcing fibers. A system of nonlinear Volterra integral equations is formulated for the dimensional changes in the block. Numerical solutions are presented for the case when the standard reinforcing model for nonlinearly elastic fiber-reinforced materials is incorporated in the Pipkin–Rogers constitutive framework. The results illustrate how the time-dependent dimensional changes depend on the fiber orientation and the viscoelastic properties of the fibers relative to those of the matrix.

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48

Berik, Pelin, e Peter L. Bishay. "Parameter Identification of the Nonlinear Piezoelectric Shear d15 Coefficient of a Smart Composite Actuator". Actuators 10, n. 7 (19 luglio 2021): 168. http://dx.doi.org/10.3390/act10070168.

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Abstract (sommario):

The objective of this work is to characterize the nonlinear dependence of the piezoelectric d15 shear coefficient of a composite actuator on the static electric field and include this effect in finite element (FE) simulations. The Levenberg-Marquardt nonlinear least squares optimization algorithm implemented in MATLAB was applied to acquire the piezoelectric shear coefficient parameters. The nonlinear piezoelectric d15 shear constant of the composite actuator integrated with piezoceramic d15 patches was obtained to be 732 pC/N at 198 V. The experimental benchmark was simulated using a three-dimensional piezoelectric FE model by taking piezoelectric nonlinearity into consideration. The results revealed that the piezoelectric shear d15 coefficient increased nonlinearly under static applied electric fields over 0.5 kV/cm. A comparison between the generated transverse deflections of the linear and nonlinear FE models was also performed.

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49

GUTSCHMIDT, STEFANIE, e ODED GOTTLIEB. "INTERNAL RESONANCES AND BIFURCATIONS OF AN ARRAY BELOW THE FIRST PULL-IN INSTABILITY". International Journal of Bifurcation and Chaos 20, n. 03 (marzo 2010): 605–18. http://dx.doi.org/10.1142/s0218127410025910.

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Abstract (sommario):

A nonlinear continuum model is used to investigate the dynamic behavior of an array of N nonlinearly coupled microbeams. Investigations concentrate on the region below the array's first pull-in instability, which is shown to be governed by several internal three-to-one and combination resonances. The nonlinear equations of motion for a two-element system are solved using the asymptotic multiple-scales method for the weak nonlinear system. The analytically obtained periodic response of two coupled microbeams is numerically evaluated by a continuation technique and complemented by a numerical analysis of a three-element array which exhibits quasi-periodic responses and lengthy chaotic transients. This study of small-size microbeam arrays serves for design purposes and the understanding of nonlinear nearest-neighbor interactions of medium- and large-size arrays.

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50

A. Jawad Almosawe, A. Jawad Almosawe, e H. L. Saadon H. L. Saadon. "Nonlinear optical and optical limiting properties of new structures of organic nonlinear optical materials for photonic applications". Chinese Optics Letters 11, n. 4 (2013): 041902–41906. http://dx.doi.org/10.3788/col201311.041902.

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