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Auteur : Grafiati
Publié le 10 mars 2023

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1

Langer, Ulrich, Sergey Repin et Monika Wolfmayr. « Functional A Posteriori Error Estimates for Parabolic Time-Periodic Boundary Value Problems ». Computational Methods in Applied Mathematics 15, no 3 (1 juillet 2015) : 353–72. http://dx.doi.org/10.1515/cmam-2015-0012.

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AbstractThe paper is concerned with parabolic time-periodic boundary value problems which are of theoretical interest and arise in different practical applications. The multiharmonic finite element method is well adapted to this class of parabolic problems. We study properties of multiharmonic approximations and derive guaranteed and fully computable bounds of approximation errors. For this purpose, we use the functional a posteriori error estimation techniques earlier introduced by S. Repin. Numerical tests confirm the efficiency of the a posteriori error bounds derived.
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2

Kudashkina, L. S., et I. L. Andronov. « Multiharmonic analysis of Mira-type stars ». Symposium - International Astronomical Union 180 (1997) : 353. http://dx.doi.org/10.1017/s0074180900131286.

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The shapes of light curves of Mira-type variable stars are analyzed by using the multi–harmonic fit (Andronov 1994). The light curves of 63 stars best covered by the AAVSO observations and published by Mattei (1978) were used. Some correlations between the characteristics of the mean light curves were found.
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3

Deng, Yinbin, et Lingyu Jin. « Exponential decay of the solutions for nonlinear multiharmonic equations ». Nonlinear Analysis : Theory, Methods & ; Applications 69, no 7 (octobre 2008) : 1953–65. http://dx.doi.org/10.1016/j.na.2007.07.036.

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4

Andronov, I. L. « Some new methods of time series analysis : Applications to the AGB stars ». Symposium - International Astronomical Union 180 (1997) : 341. http://dx.doi.org/10.1017/s0074180900131183.

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Some supplementary methods of time series analysis are described which are used for study of periodic and aperiodic variability of the AGB stars. These are “multiharmonic fits” used to fit the periodic (asinusoidal) curve; running approximations – “parabolae”, “sines”; “asymptotic parabolae”; “linear fits”.
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5

Cardona, Alberto, Thierry Coune, Albert Lerusse et Michel Geradin. « A multiharmonic method for non-linear vibration analysis ». International Journal for Numerical Methods in Engineering 37, no 9 (15 mai 1994) : 1593–608. http://dx.doi.org/10.1002/nme.1620370911.

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6

Bachinger, F., U. Langer et J. Schöberl. « Numerical analysis of nonlinear multiharmonic eddy current problems ». Numerische Mathematik 100, no 4 (3 mai 2005) : 593–616. http://dx.doi.org/10.1007/s00211-005-0597-2.

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7

Petrov, E. P. « A Method for Use of Cyclic Symmetry Properties in Analysis of Nonlinear Multiharmonic Vibrations of Bladed Disks ». Journal of Turbomachinery 126, no 1 (1 janvier 2004) : 175–83. http://dx.doi.org/10.1115/1.1644558.

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An effective method for analysis of periodic forced response of nonlinear cyclically symmetric structures has been developed. The method allows multiharmonic forced response to be calculated for a whole bladed disk using a periodic sector model without any loss of accuracy in calculations and modeling. A rigorous proof of the validity of the reduction of the whole nonlinear structure to a sector is provided. Types of bladed disk forcing for which the method may be applied are formulated. A multiharmonic formulation and a solution technique for equations of motion have been derived for two cases of description for a linear part of the bladed disk model: (i) using sector finite element matrices and (ii) using sector mode shapes and frequencies. Calculations validating the developed method and a numerical investigation of a realistic high-pressure turbine bladed disk with shrouds have demonstrated the high efficiency of the method.
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8

Kolmbauer, Michael, et Ulrich Langer. « A Robust Preconditioned MinRes Solver for Time-periodic Eddy Current Problems ». Computational Methods in Applied Mathematics 13, no 1 (1 janvier 2013) : 1–20. http://dx.doi.org/10.2478/cmam-2012-0023.

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Abstract.This work is devoted to fast and parameter-robust iterative solvers for frequency domain finite element equations, approximating the time-periodic eddy current problem with multiharmonic or time-periodic excitations in time. We construct a preconditioned MinRes solver for the frequency domain equations, that is robust with respect to the discretization parameters as well as all involved “bad” parameters like the conductivity, the reluctivity and possible regularization parameters.
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9

Berthillier, M., C. Dupont, R. Mondal et J. J. Barrau. « Blades Forced Response Analysis With Friction Dampers ». Journal of Vibration and Acoustics 120, no 2 (1 avril 1998) : 468–74. http://dx.doi.org/10.1115/1.2893853.

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A multiharmonic frequency domain analysis combined with a Craig-Bampton component mode synthesis is presented to compute the dry friction damped forced response of blades. The accuracy of the analysis is established, for a cantilever beam with a dry friction damper attached, by comparison with experimental results and time domain analysis. The method has then been applied to a model fan blade damped by a blade to ground damper.
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10

Chen, Jingfeng, Wenzhi Wang, Chong He, Yajun Li, Xianling Liang, Junping Geng et Ronghong Jin. « Direction Finding Based on Time-Modulated Array With Multiharmonic Analysis ». IEEE Transactions on Antennas and Propagation 68, no 7 (juillet 2020) : 5753–58. http://dx.doi.org/10.1109/tap.2020.2969972.

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11

Solomou, M., D. Rees et N. Chiras. « Frequency Domain Analysis of Nonlinear Systems Driven by Multiharmonic Signals ». IEEE Transactions on Instrumentation and Measurement 53, no 2 (avril 2004) : 243–50. http://dx.doi.org/10.1109/tim.2003.822477.

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12

Petrov, E. P., et D. J. Ewins. « Advanced Modeling of Underplatform Friction Dampers for Analysis of Bladed Disk Vibration ». Journal of Turbomachinery 129, no 1 (1 février 2006) : 143–50. http://dx.doi.org/10.1115/1.2372775.

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Advanced structural dynamic models for both wedge and split underplatform dampers have been developed. The new damper models take into account inertia forces and the effects of normal load variation on stick-slip transitions at the contact interfaces. The damper models are formulated for the general case of multiharmonic forced response analysis. An approach for using the new damper models in the dynamic analysis of large-scale finite element models of bladed disks is proposed and realized. Numerical investigations of bladed disks are performed to demonstrate the capabilities of the new models and an analysis of the influence of the damper parameters on the forced response of bladed disks is made.
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13

Petrov, E. P., et D. J. Ewins. « Effects of Damping and Varying Contact Area at Blade-Disk Joints in Forced Response Analysis of Bladed Disk Assemblies ». Journal of Turbomachinery 128, no 2 (28 septembre 2005) : 403–10. http://dx.doi.org/10.1115/1.2181998.

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An approach is developed to analyze the multiharmonic forced response of large-scale finite element models of bladed disks taking account of the nonlinear forces acting at the contact interfaces of blade roots. Area contact interaction is modeled by area friction contact elements which allow for friction stresses under variable normal load, unilateral contacts, clearances, and interferences. Examples of application of the new approach to the analysis of root damping and forced response levels are given and numerical investigations of effects of contact conditions at root joints and excitation levels are explored for practical bladed disks.
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14

NASSAR, I. N., et ROBERT HORTON. « DETERMINATION OF SOIL APPARENT THERMAL DIFFUSIVITY FROM MULTIHARMONIC TEMPERATURE ANALYSIS FOR NONUNIFORM SOILS ». Soil Science 149, no 3 (mars 1990) : 125–30. http://dx.doi.org/10.1097/00010694-199003000-00001.

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15

CHEN, J., T. FABER, C. COOKE et E. GARCIA. « Temporal resolution of multiharmonic phase analysis of ECG-gated myocardial perfusion SPECT studies ». Journal of Nuclear Cardiology 15, no 3 (mai 2008) : 383–91. http://dx.doi.org/10.1016/j.nuclcard.2008.02.014.

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16

Shang, Y., H. Xu, J. Mo, Z. Wang, X. Xu, Z. Tu, X. Zhang, H. Zheng, W. Chen et F. Yu. « The Design and Thermal Reliability Analysis of a High-Efficiency K-Band MMIC Medium-Power Amplifier with Multiharmonic Matching ». Active and Passive Electronic Components 2016 (2016) : 1–7. http://dx.doi.org/10.1155/2016/6295405.

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A new high-efficiency K-band MMIC medium-power amplifier (PA) is designed with multiharmonic matching using GaAs pHEMT process technology. It has an operation frequency centered at 26 GHz with a bandwidth of 2 GHz. A 20 dBm 1 dB-compression-point output power and 40% efficiency are achieved. A novel thermal reliability analysis method based on ICEPAK is proposed also to evaluate its thermal characteristic. The test result by using a QFI InfraScope™infrared imaging system is compared with the simulation result. It agrees well with an accuracy within ±1°C differences, which reflects the advantages of the thermal analysis method with respect to accuracy and convenience for use.
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17

VALETTE, H., M. H. BOURGUIGNON, P. MERLET, M.-C. GR??GOIRAE, P. BRIANDET et A. SYROTA. « The value of pixel per pixel multiharmonic Fourier analysis to assess left ventricular function ». Nuclear Medicine Communications 13, no 3 (mars 1992) : 137–41. http://dx.doi.org/10.1097/00006231-199203000-00003.

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18

Petrov, E. P. « Method for Direct Parametric Analysis of Nonlinear Forced Response of Bladed Disks With Friction Contact Interfaces ». Journal of Turbomachinery 126, no 4 (1 octobre 2004) : 654–62. http://dx.doi.org/10.1115/1.1776588.

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An effective method for direct parametric analysis of periodic nonlinear forced response of bladed disks with friction contact interfaces has been developed. The method allows, forced response levels to be calculated directly as a function of contact interface parameters such as the friction coefficient, contact surface stiffness (normal and tangential coefficients), clearances, interferences, and the normal stresses at the contact interfaces. The method is based on exact expressions for sensitivities of the multiharmonic interaction forces with respect to variation of all parameters of the friction contact interfaces. These novel expressions are derived in the paper for a friction contact model, accounting for the normal load variation and the possibility of separation-contact transitions. Numerical analysis of effects of the contact parameters on forced response levels has been performed using large-scale finite element models of a practical bladed turbine disk with underplatform dampers and with shroud contacts.
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19

Liu, Guohai, Huan Zhong, Liang Xu et Wenxiang Zhao. « Analysis and Evaluation of a Linear Primary Permanent Magnet Vernier Machine With Multiharmonics ». IEEE Transactions on Industrial Electronics 68, no 3 (mars 2021) : 1982–93. http://dx.doi.org/10.1109/tie.2020.2973888.

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20

ROUZET, F., P. LIM, L. SARDAMANTEL, S. BLEICHNERPEREZ, D. LASALMONIE, M. SLAMA, A. COHENSOLAL et D. LEGULUDEC. « Impact of cardiac resynchronization therapy on ventricular delays assessed by multiharmonic analysis of radionuclide angiography ». Journal of Nuclear Cardiology 12, no 2 (mars 2005) : S39. http://dx.doi.org/10.1016/j.nuclcard.2004.12.148.

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21

Kolmbauer, M. « Efficient solvers for multiharmonic eddy current optimal control problems with various constraints and their analysis ». IMA Journal of Numerical Analysis 33, no 3 (31 octobre 2012) : 1063–94. http://dx.doi.org/10.1093/imanum/drs025.

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22

Petrov, E. P., et D. J. Ewins. « Method for Analysis of Nonlinear Multiharmonic Vibrations of Mistuned Bladed Disks With Scatter of Contact Interface Characteristics ». Journal of Turbomachinery 127, no 1 (1 janvier 2005) : 128–36. http://dx.doi.org/10.1115/1.1812781.

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An efficient method for analysis of nonlinear vibrations of mistuned bladed disk assemblies has been developed. This development has facilitated the use of large-scale finite element models for realistic bladed disks, used hitherto in analysis of linear vibration, to be extended for the analysis of nonlinear multiharmonic vibration. The new method is based on a technique for the exact condensation of nonlinear finite element models of mistuned bladed disks. The model condensation allows the size of the nonlinear equations to be reduced to the number of degrees of freedom where nonlinear interaction forces are applied. The analysis of nonlinear forced response for simplified and realistic models of mistuned bladed disks has been performed. For a practical high-pressure bladed turbine disk, several types of nonlinear forced response have been considered, including mistuning by (i) scatter of underplatform dampers, (ii) shroud gap scatter, and (iii) blade frequency scatter in the presence of nonlinear shroud interactions.
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23

Spagnolo, Sandro, Eric S. Muckley, Ilia N. Ivanov et Tibor Hianik. « Analysis of trypsin activity at β-casein layers formed on hydrophobic surfaces using a multiharmonic acoustic method ». Analyst 147, no 3 (2022) : 461–70. http://dx.doi.org/10.1039/d1an01800k.

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For processing the changes in the fundamental frequency (8 MHz) and dissipation parameter of a crystal coated with dodecanethiol after the addition of β-casein and its cleavage by trypsin at different concentrations (0.3 nM–20 nM), a model was developed to study the enzyme activity and the physical properties of the protein layer.
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24

Belkourchia, Yassin, et Lahcen Azrar. « A New Numerical Procedure for Vibration Analysis of Beam under Impulse and Multiharmonics Piezoelectric Actuators ». Journal of Applied Mathematics 2020 (28 août 2020) : 1–19. http://dx.doi.org/10.1155/2020/7391848.

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The dynamic behavior of structures with piezoelectric patches is governed by partial differential equations with strong singularities. To directly deal with these equations, well adapted numerical procedures are required. In this work, the differential quadrature method (DQM) combined with a regularization procedure for space and implicit scheme for time discretization is used. The DQM is a simple method that can be implemented with few grid points and can give results with a good accuracy. However, the DQM presents some difficulties when applied to partial differential equations involving strong singularities. This is due to the fact that the subsidiaries of the singular functions cannot be straightforwardly discretized by the DQM. A methodological approach based on the regularization procedure is used here to overcome this difficulty and the derivatives of the Dirac-delta function are replaced by regularized smooth functions. Thanks to this regularization, the resulting differential equations can be directly discretized using the DQM. The efficiency and applicability of the proposed approach are demonstrated in the computation of the dynamic behavior of beams for various boundary conditions and excited by impulse and Multiharmonics piezoelectric actuators. The obtained numerical results are well compared to the developed analytical solution.
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Spagnolo, Sandro, Eric S. Muckley, Ilia N. Ivanov et Tibor Hianik. « Application of Multiharmonic QCM-D for Detection of Plasmin at Hydrophobic Surfaces Modified by β-Casein ». Chemosensors 10, no 4 (11 avril 2022) : 143. http://dx.doi.org/10.3390/chemosensors10040143.

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Plasmin protease plays an important role in many processes in living systems, including milk. Monitoring plasmin activity is important for control of the nutritional quality of milk and other dairy products. We designed a biosensor to detect the proteolytic activity of plasmin, using multiharmonic quartz crystal microbalance with dissipation (QCM-D). The β-casein immobilized on the hydrophobic surface of 1-dodecanethiol on the AT-cut quartz crystal was used to monitor plasmin activity. We demonstrated detection of plasmin in a concentration range of 0.1–20 nM, with the limit of detection about 0.13 ± 0.01 nM. The analysis of viscoelastic properties of the β-casein layer showed rapid changes of shear elasticity modulus, μ, and coefficient of viscosity, η, at plasmin sub-nanomolar concentrations, followed by modest changes at nanomolar concentrations, indicating multilayer architecture β-casein. A comparative analysis of viscoelastic properties of β-casein layers following plasmin and trypsin cleavage showed that the higher effect of trypsin was due to larger potential cleavage sites of β-casein.
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26

DAOU, D., R. LEBTAHI, M. FARAGGI, Y. PETEGNIEF et D. LEGULUDEC. « Cardiac gated equilibrium radionuclide angiography and multiharmonic Fourier phase analysis : Optimal acquisition parameters in arrhythmogenic right ventricular cardiomyopathy ». Journal of Nuclear Cardiology 6, no 4 (juillet 1999) : 429–37. http://dx.doi.org/10.1016/s1071-3581(99)90009-0.

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Machac, Josef, Steven F. Horowitz, Richard Fagerstrom, Rebecca Levine et Stanley J. Goldsmith. « Characterization and automatic identification of ECG conduction abnormalities using segmental multiharmonic fourier analysis of gated blood-pool scintigrams ». European Journal of Nuclear Medicine 11-11, no 6-7 (novembre 1985) : 210–16. http://dx.doi.org/10.1007/bf00279071.

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28

Mashayekhi, Fahimeh, Stefano Zucca et Ali S. Nobari. « Evaluation of free interface-based reduction techniques for nonlinear forced response analysis of shrouded blades ». Proceedings of the Institution of Mechanical Engineers, Part C : Journal of Mechanical Engineering Science 233, no 23-24 (31 août 2019) : 7459–75. http://dx.doi.org/10.1177/0954406219872523.

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The efficient dynamic stress assessment of turbine blades is of prime importance in turbomachinery design. An accurate prediction of forced response level of shrouded blades requires a very detailed finite element model in addition to a nonlinear solver. In order to perform nonlinear forced response analysis of blades at an affordable computational cost, applying a model order reduction technique is essential. The appeal for component mode synthesis methods in dimension reduction of structures with friction contacts is due to the possibility of retaining a subset of physical degrees of freedom (e.g. the contact degrees of freedom) in the set of generalized coordinates. In this paper, a reduction method recently developed for nonlinear forced response analysis of structures with local nonlinearity is evaluated and compared with two classical component mode synthesis reduction techniques. All three methods have the same projection basis, which includes residual flexibility attachment modes and free interface modes, but different implementation. The response is computed in the frequency domain using multiharmonic balance method and periodic contact forces are modeled with a node-to-node 3D friction contact model. In order to demonstrate the efficiency of the three formulations, a rod and a simplified shrouded turbine blade are considered as case studies.
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Liu, Jiuzhou, Lin Li, Yu Fan et Xingrong Huang. « A Modified Nonlinear Modal Synthesis Scheme for Mistuned Blisks with Synchronized Switch Damping ». International Journal of Aerospace Engineering 2018 (12 juillet 2018) : 1–15. http://dx.doi.org/10.1155/2018/8517890.

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In the authors’ previous work (MSSP 2017), we show that the synchronized switch damping based on negative capacitor (SSDNC) is a good candidate for vibration suppression of tuned blisks. In this paper, we consider the mistuned case and propose an efficient numerical approach to accelerate the required statistical analysis. Although SSDNC is a type of nonlinear piezoelectric damping, through an in-depth nonlinear modal analysis, we show that the modal information of the system remains unchanged with respect to the nonlinear modal amplitude. Based on this, an accelerated nonlinear component modal synthesis (NCMS) method is proposed to predict and further analyse the dynamic characteristics of the nonlinear system. The precision and efficiency of the proposed method is compared with that of the multiharmonic balance method. The stochastic characteristics of the blisk are studied with two sources of mistuning. The first one is random stiffness mistuning and the second one is capacitance mistuning. The investigation is carried out with different mistuning levels and under different engine-order excitations. The results show that the NCMS method can accurately predict the forced response of the mistuned blisk with SSDNC, and the calculation cost can be considerably reduced. Two advantages of the SSDNC technique applied to the mistuned blisk have been revealed in the statistical view. The first one is that the SSDNC can suppress the amplified vibration induced by the mistuning of the blisk significantly. The second one is that the vibration-suppression performance of SSDNC is insensitive to the mistuning of the blisk and that of the electrical circuits.
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30

Krumbholz, Katrin, et Sabine Schmidt. « Evidence for an analytic perception of multiharmonic sounds in the bat, Megaderma lyra, and its possible role for echo spectral analysis ». Journal of the Acoustical Society of America 109, no 4 (avril 2001) : 1705–16. http://dx.doi.org/10.1121/1.1354198.

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31

Setter, Eyal, Izhak Bucher et Shimon Haber. « Propulsion at low Reynolds numbers by multiple traveling waves ». Proceedings of the Institution of Mechanical Engineers, Part C : Journal of Mechanical Engineering Science 228, no 16 (12 février 2014) : 2938–49. http://dx.doi.org/10.1177/0954406214523580.

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Microorganisms or micro-robotic swimmers employ traveling waves as a common swimming mechanism involving time-irreversible deformations of their outer surface. Normally, the deforming surfaces constitute of multiple spatial waves, some standing and others propagating forward or backward. A unique technique is developed here to experimentally decompose a waving surface into its spatial wavelengths in each time instance by processing a sequence of photographs. This information is curve fitted to yield the phase velocity, frequency, and amplitudes of the propagating and receding waves of each component. The significance of the harmonic decomposition is demonstrated using an experimental macro-scale swimmer that utilizes small amplitude circumferential waves. A numerical image processing and curve-fitting procedure is shown and a theoretical model is also developed to account for the hydrodynamic effects of multiple wavelengths. The theoretical results fit well with the experimental data at low speeds, although the contribution of higher harmonics was small in experiment, but the higher harmonics are clearly visible and successfully identified. Still, the importance of the multiharmonics analysis for swimmers, which utilize traveling waves mechanisms, found both in nature and in man-made machines, was formulated and partially verified.
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32

Mondrik, N., J. P. Long et J. L. Marshall. « A MULTIBAND GENERALIZATION OF THE MULTIHARMONIC ANALYSIS OF VARIANCE PERIOD ESTIMATION ALGORITHM AND THE EFFECT OF INTER-BAND OBSERVING CADENCE ON PERIOD RECOVERY RATE ». Astrophysical Journal 811, no 2 (29 septembre 2015) : L34. http://dx.doi.org/10.1088/2041-8205/811/2/l34.

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33

Reutov, V. P., et G. V. Rybushkina. « Unsteady chains of wave structures and anomalous transport of а passive scalar in a barotropic jet flow ». Известия Российской академии наук. Физика атмосферы и океана 55, no 6 (21 décembre 2019) : 201–10. http://dx.doi.org/10.31857/s0002-3515556201-210.

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The onset of anomalous transport of a passive scalar at the excitation of unsteady chains of wave structures with closed streamlines in a barotropic jet flow modeling zonal flows in the Earths atmosphere and ocean and in laboratory experiments is investigated. The analysis is performed within a dynamical model describing saturation of the barotropic instability in a plane-parallel channel flow with allowance for the beta-effect and external friction. The equations of a quasi-two-dimensional flow are solved numerically with the aid of a pseudospectral method. It is found that the generation of high modes in a jet with a two-hump velocity profile leads to accelerated transition to the complex dynamics, at which an increase in supercriticality first gives rise to а multiharmonic regime with a discrete spectrum. The exponents of the power dependence on the time of the averaged (over the ensemble) tracer particle displacement and its variance are computed for the basic generation regimes, which confirms the occurrence of anomalous diffusion of the scalar. A self-similar probability density function of tracer displacements is obtained and the dependence of the transition to complex dynamics on the number of vortices in the chain and on the strength of the beta-effect is elucidated. Numerical estimates are presented, which confirm the possibility of generation of unsteady vortex chains and the related anomalous transport of the scalar.barotropic flow; chains of wave structures; dynamical chaos; anomalous advection and diffusion
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Tatarko, Marek, Sandro Spagnolo, Veronika Oravczová, Judit Süle, Milan Hun, Attila Hucker et Tibor Hianik. « Changes of Viscoelastic Properties of Aptamer-Based Sensing Layers Following Interaction with Listeria innocua ». Sensors 21, no 16 (19 août 2021) : 5585. http://dx.doi.org/10.3390/s21165585.

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A multiharmonic quartz crystal microbalance (QCM) has been applied to study the viscoelastic properties of the aptamer-based sensing layers at the surface of a QCM transducer covered by neutravidin following interaction with bacteria Listeria innocua. Addition of bacteria in the concentration range 5 × 103–106 CFU/mL resulted in a decrease of resonant frequency and in an increase of dissipation. The frequency decrease has been lower than one would expect considering the dimension of the bacteria. This can be caused by lower penetration depth of the acoustics wave (approximately 120 nm) in comparison with the thickness of the bacterial layer (approximately 500 nm). Addition of E. coli at the surface of neutravidin as well as aptamer layers did not result in significant changes in frequency and dissipation. Using the Kelvin–Voight model the analysis of the viscoelastic properties of the sensing layers was performed and several parameters such as penetration depth, Γ, viscosity coefficient, η, and shear modulus, μ, were determined following various modifications of QCM transducer. The penetration depth decreased following adsorption of the neutravidin layer, which is evidence of the formation of a rigid protein structure. This value did not change significantly following adsorption of aptamers and Listeria innocua. Viscosity coefficient was higher for the neutravidin layer in comparison with the naked QCM transducer in a buffer. However, a further increase of viscosity coefficient took place following attachment of aptamers suggesting their softer structure. The interaction of Listeria innocua with the aptamer layer resulted in slight decrease of viscosity coefficient. The shearing modulus increased for the neutravidin layer and decreased following aptamer adsorption, while a slight increase of µ was observed after the addition of Listeria innocua.
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35

Taghavi, Seyed Farid. « A Fourier-cumulant analysis for multiharmonic flow fluctuation ». European Physical Journal C 81, no 7 (juillet 2021). http://dx.doi.org/10.1140/epjc/s10052-021-09413-0.

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AbstractThe Fourier analysis of the final particle distribution followed by cumulant study of the Fourier coefficient event-by-event fluctuation is one of the main approaches for testing the collective evolution in the heavy-ion collision. Using a multidimensional generating function, we propose a method to extract any possible cumulant of multiharmonic flow fluctuations and classify them in terms of the order of cumulants and harmonics involved in them. In particular, we show that there are 33 distinct cumulants with order 2, 3, 4, 5 and harmonics 2, 3, 4, 5. We compute the normalized version of these cumulants from hydrodynamic simulation for Pb–Pb collisions based on $$_\mathtt{R}$$ R ++. We compare the simulation with those normalized cumulants that the LHC has measured and predict the unmeasured ones. Comparing the initial and final state fluctuation normalized cumulants, we compute the linear and nonlinear hydrodynamic response couplings. We finally introduce the genuine three-particle correlation function containing information of all third-order cumulants.
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36

Petrov, E. P. « Analytical Formulation of Friction Contact Elements for Frequency-Domain Analysis of Nonlinear Vibrations of Structures With High-Energy Rubs ». Journal of Engineering for Gas Turbines and Power 141, no 12 (8 novembre 2019). http://dx.doi.org/10.1115/1.4045183.

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Abstract In gas-turbine engines and other rotating machinery structures, rubbing contact interactions can occur when the contacting components have large relative motion between components: such as in rotating bladed disk-casing rubbing contacts, and rubbing in rotor bearing and labyrinth seals. The analysis of vibrations of structures with rubbing contacts requires the development of a mathematical model and special friction contact elements that would allow for the prescribed relative motion of rubbing surfaces in addition to the motion due to vibrations of the contacting components. In the proposed paper, the formulation of the friction contact elements is developed, which includes the effects of the prescribed relative motion on the friction stick-slip transitions and, therefore, on the contact interaction forces. For a first time, the formulation is made for the frequency domain analysis of coupled rubbing and vibrational motion, using the multiharmonic representation of the vibration displacements. The formulation is made fully analytically to express the multiharmonic contact interaction forces and multiharmonic tangent stiffness matrix in an explicit analytical form allowing their calculation accurately and fast. The dependency of the friction and contact stiffness coefficients on the energy dissipated during high-energy rubbing contacts and, hence, on the corresponding increase of the contact interface temperature is included in the formulation. The efficiency of the developed friction elements is demonstrated on a set of test cases including simple models and a large-scale realistic blade.
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37

Petrov, E. P. « Analysis of Bifurcations in Multiharmonic Analysis of Nonlinear Forced Vibrations of Gas Turbine Engine Structures With Friction and Gaps ». Journal of Engineering for Gas Turbines and Power 138, no 10 (12 avril 2016). http://dx.doi.org/10.1115/1.4032906.

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An efficient frequency-domain method has been developed to analyze the forced response of large-scale nonlinear gas turbine structures with bifurcations. The method allows detection and localization of the design and operating conditions sets where bifurcations occur, calculation of tangents to the solution trajectory, and continuation of solutions under parameter variation for structures with bifurcations. The method is aimed at calculation of steady-state periodic solution, and multiharmonic representation of the variation of displacements in time is used. The possibility of bifurcations in realistic gas-turbine structures with friction contacts and with cubic nonlinearity has been shown.
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38

Siewert, Christian, Lars Panning, Jörg Wallaschek et Christoph Richter. « Multiharmonic Forced Response Analysis of a Turbine Blading Coupled by Nonlinear Contact Forces ». Journal of Engineering for Gas Turbines and Power 132, no 8 (26 mai 2010). http://dx.doi.org/10.1115/1.4000266.

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In turbomachinery applications, the rotating turbine blades are subjected to high static and dynamic loads. The static loads are due to centrifugal stresses and thermal strains whereas the dynamic loads are caused by the fluctuating gas forces resulting in high vibration amplitudes, which can lead to high cycle fatigue failures. Hence, one of the main tasks in the design of turbomachinery blading is the reduction in the blade vibration amplitudes to avoid high dynamic stresses. Thus, coupling devices like underplatform dampers and tip shrouds are applied to the blading to reduce the vibration amplitudes and, therefore, the dynamic stresses by introducing nonlinear contact forces to the system. In order to predict the resulting vibration amplitudes, a reduced order model of a shrouded turbine blading is presented including a contact model to determine the nonlinear contact forces. To compute the forced response, the resulting nonlinear equations of motion are solved in the frequency domain using the multiharmonic balance method because of the high computational efficiency of this approach. The transformation from the time domain into the frequency domain is done by applying Galerkin’s method in combination with a multiharmonic approximation function for the unknown vibration response. This results in an algebraic system of nonlinear equations in the frequency domain, which has to be solved iteratively in order to compute the vibration response. The presented methodology is applied to the calculation of the forced response of a nonlinear coupled turbine blading in the frequency domain.
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39

Langer, U., et M. Wolfmayr. « Multiharmonic finite element analysis of a time-periodic parabolic optimal control problem ». Journal of Numerical Mathematics 21, no 4 (janvier 2013). http://dx.doi.org/10.1515/jnum-2013-0011.

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40

Petrov, E. P. « Stability Analysis of Multiharmonic Nonlinear Vibrations for Large Models of Gas Turbine Engine Structures With Friction and Gaps ». Journal of Engineering for Gas Turbines and Power 139, no 2 (20 septembre 2016). http://dx.doi.org/10.1115/1.4034353.

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An efficient method is proposed for the multiharmonic frequency-domain analysis of the stability for nonlinear periodic forced vibrations in gas turbine engine structures and turbomachines with friction, gaps, and other types of nonlinear contact interfaces. The method allows using large-scale finite element models for structural components together with detailed description of nonlinear interactions at contact interfaces between these components. The highly accurate reduced models are applied in the assessment of stability of periodic regimes for large-scale model of gas turbine structures. An approach is proposed for the highly accurate calculation of motion of a structure after it is perturbed from the periodic nonlinear forced response. Efficiency of the developed approach is demonstrated on a set of test cases including simple models and large-scale realistic bladed disk models with different types of nonlinearities: friction, gaps, and cubic nonlinear springs.
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41

Wei, F., et G. T. Zheng. « Multiharmonic Response Analysis of Systems With Local Nonlinearities Based on Describing Functions and Linear Receptance ». Journal of Vibration and Acoustics 132, no 3 (22 avril 2010). http://dx.doi.org/10.1115/1.4000781.

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Direct time integration methods are usually applied to determine the dynamic response of systems with local nonlinearities. Nevertheless, these methods are computationally expensive to predict the steady state response. To significantly reduce the computational effort, a new approach is proposed for the multiharmonic response analysis of dynamical systems with local nonlinearities. The approach is based on the describing function (DF) method and linear receptance data. With the DF method, the kinetic equations are converted into a set of complex algebraic equations. By using the linear receptance data, the dimension of the complex algebraic equations, which should be solved iteratively, are only related to nonlinear degrees of freedom (DOFs). A cantilever beam with a local nonlinear element is presented to show the procedure and performance of the proposed approach. The approach can greatly reduce the size and computational cost of the problem. Thus, it can be applicable to large-scale systems with local nonlinearities.
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42

Koscso, Adam, et Evgeny Petrov. « Sensitivity and Forced Response Analysis of Anisotropy-Mistuned Bladed Disks With Nonlinear Contact Interfaces ». Journal of Engineering for Gas Turbines and Power 141, no 10 (26 septembre 2019). http://dx.doi.org/10.1115/1.4044883.

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AbstractA new method has been developed for the analysis of nonlinear forced response of bladed disks mistuned by blade anisotropy scatter and for the forced response sensitivity to blade material anisotropy orientations. The approach allows for the calculation of bladed disks with nonlinear friction contact interfaces using the multiharmonic balance method. The method uses efficient high-accuracy model reduction method for the minimization of the computational effort while providing required accuracy. The capabilities of the developed methods are validated and demonstrated using a two-blade model. A thorough study of the influence of the material anisotropy mistuning and its sensitivity on the characteristics of the forced response is carried out using finite element (FE) modes of anisotropy mistuned realistic bladed disk with nonlinear friction joints of blade roots and shroud contacts. The dependency of the nonlinear forced response on excitation level and contact pressure values has been carried out for anisotropy mistuned bladed disks.
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43

Petrov, E. P. « Explicit Finite Element Models of Friction Dampers in Forced Response Analysis of Bladed Disks ». Journal of Engineering for Gas Turbines and Power 130, no 2 (25 février 2008). http://dx.doi.org/10.1115/1.2772633.

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A generic method for analysis of nonlinear forced response for bladed disks with friction dampers of different designs has been developed. The method uses explicit finite element modeling of dampers, which allows accurate description of flexibility and, for the first time, dynamic properties of dampers of different designs in multiharmonic analysis of bladed disks. Large-scale finite element damper and bladed disk models containing 104−106 degrees of freedom can be used. These models, together with detailed description of contact interactions over contact interface areas, allow for any level of refinement required for modeling of elastic damper bodies and for modeling of friction contact interactions. Numerical studies of realistic bladed disks have been performed with three different types of underplatform dampers: (i) a “cottage-roof” (also called “wedge”) damper, (ii) seal wire damper, and (iii) a strip damper. Effects of contact interface parameters and excitation levels on damping properties of the dampers and forced response are extensively explored.
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44

Kim, Sunghoon, Joon-Hyuk Ko et Wonho Jhe. « Universal Theory of Dynamic Force Microscopy for Exact and Robust Force Reconstruction Using Multiharmonic Signal Analysis ». Physical Review Letters 126, no 7 (19 février 2021). http://dx.doi.org/10.1103/physrevlett.126.076804.

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45

Petrov, E. P. « Frequency-Domain Sensitivity Analysis of Stability of Nonlinear Vibrations for High-Fidelity Models of Jointed Structures ». Journal of Engineering for Gas Turbines and Power 140, no 1 (19 septembre 2017). http://dx.doi.org/10.1115/1.4037708.

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For the analysis of essentially nonlinear vibrations, it is very important not only to determine whether the considered vibration regime is stable or unstable but also which design parameters need to be changed to make the desired stability regime and how sensitive is the stability of a chosen design of a gas-turbine structure to variation of the design parameters. In the proposed paper, an efficient method is proposed for a first time for sensitivity analysis of stability for nonlinear periodic forced response vibrations using large-scale models structures with friction, gaps, and other types of nonlinear contact interfaces. The method allows using large-scale finite element (FE) models for structural components together with detailed description of nonlinear interactions at contact interfaces. The highly accurate reduced models are applied in the assessment of the sensitivity of stability of periodic regimes. The stability sensitivity analysis is performed in frequency domain with the multiharmonic representation of the nonlinear forced response amplitudes. Efficiency of the developed approach is demonstrated on a set of test cases including simple models and large-scale realistic blade model with different types of nonlinearities, including friction, gaps, and cubic elastic nonlinearity.
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46

Wang, Zhaoliang, Zhe Xu, Xiaoli Du et Dawei Tang. « Multiharmonics Method Characterizing In-Plane Thermal Conductivity and TBR of Semiconductor Nanofilm on Substrate : Theoretical Analysis ». International Journal of Thermophysics 38, no 2 (19 décembre 2016). http://dx.doi.org/10.1007/s10765-016-2147-9.

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47

Yoon, Yongsoon, et Avra Brahma. « Air–Fuel Ratio Imbalance Diagnostic of Spark-Ignited Engines With Modulated Sliding Discrete Fourier Transform ». Journal of Dynamic Systems, Measurement, and Control 142, no 8 (18 mars 2020). http://dx.doi.org/10.1115/1.4046550.

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Abstract This paper presents the novel on-board air–fuel ratio (AFR) imbalance diagnostic of spark-ignited (SI) engines. Because of the reciprocating nature of internal combustion engines, while this fault is present, it is known that the exhaust gas oxygen (EGO) sensor signal is accompanied by the oscillating disturbance of which frequency depends on the engine speed, such that it can be represented by the superposition of multiharmonic and DC signals. Motivated from this inherent feature, the novel diagnostic for detection and location of AFR imbalance is developed with modulated sliding discrete Fourier transform (mSDFT) and angular domain sampling. The feasibility is demonstrated with the simulated and measured AFR signals. It turns out that the developed diagnostic is able to identify fault types such as lean or rich imbalance and locate a single cylinder or multiple cylinders having abnormal AFR. It is robust to measurement noise at the expense of slow convergence rate. Spectral leakage is reduced with crank domain sampling such that accuracy in spectral analysis is improved. Finally, the diagnostic has great potential for broad reciprocating machinery.
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48

Petrov, E. P. « A Method for Parametric Analysis of Stability Boundaries for Nonlinear Periodic Vibrations of Structures With Contact Interfaces ». Journal of Engineering for Gas Turbines and Power 141, no 3 (29 octobre 2018). http://dx.doi.org/10.1115/1.4040850.

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A method for parametric analysis of the stability loss boundary has been developed for periodic regimes of nonlinear forced vibrations for a first time. The method allows parametric frequency-domain calculations of the stability loss together with the vibration amplitudes and design parameter values corresponding to the stability boundaries. The tracing algorithm is applied to obtain the trajectories of stability loss points as functions of design parameters. The parametric stability loss is formulated for cases when (i) the design parameters characterize the properties of nonlinear contact interfaces (e.g., gap, contact stiffness, and friction coefficient); (ii) the design parameters describe linear components of the analyzed structure (e.g., parameters of geometric shape, material, natural frequencies, and modal damping); and (iii) these parameters describe the excitation loads (e.g., their level, distribution or frequency). An approach allowing the multiparametric analysis of stability boundaries is proposed. The method uses the multiharmonic representation of the periodic forced response and aimed at the analysis of realistic gas-turbine structures comprising thousands and millions degrees-of-freedom (DOF). The method can be used for the effective search of isolated branches of the nonlinear solutions and examples of detection and search of the isolated branches are given: for relatively small and for large-scale finite element (FE) models. The efficiency of the method for calculation of the stability boundaries and for the search of isolated branches is demonstrated on simple systems and on a large-scale model of a turbine blade.
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49

Saito, Akira, Matthew P. Castanier, Christophe Pierre et Olivier Poudou. « Efficient Nonlinear Vibration Analysis of the Forced Response of Rotating Cracked Blades ». Journal of Computational and Nonlinear Dynamics 4, no 1 (11 novembre 2008). http://dx.doi.org/10.1115/1.3007908.

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The efficient nonlinear vibration analysis of a rotating elastic structure with a crack is examined. In particular, the solution of the forced vibration response of a cracked turbine engine blade is investigated. Starting with a finite element model of the cracked system, the Craig–Bampton method of component mode synthesis is used to generate a reduced-order model that retains the nodes of the crack surfaces as physical degrees of freedom. The nonlinearity due to the intermittent contact of the crack surfaces, which is caused by the opening and closing of the crack during each vibration cycle, is modeled with a piecewise linear term in the equations of motion. Then, the efficient solution procedure for solving the resulting nonlinear equations of motion is presented. The approach employed in this study is a multiharmonic hybrid frequency∕time-domain technique, which is an extension of the traditional harmonic balance method. First, a simple beam model is used to perform a numerical validation by comparing the results of the new method to those from transient finite element analysis (FEA) with contact elements. It is found that the new method retains good accuracy relative to FEA while reducing the computational costs by several orders of magnitude. Second, a representative blade model is used to examine the effects of crack length and rotation speed on the resonant frequency response. Several issues related to the rotation are investigated, including geometry changes of the crack, shifts in resonant frequencies, and the existence of multiple solutions. For the cases considered, it is found that the nonlinear vibration response exhibits the jump phenomenon only when rotation is included in the model.
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50

Fronk, Matthew D., et Michael J. Leamy. « Higher-Order Dispersion, Stability, and Waveform Invariance in Nonlinear Monoatomic and Diatomic Systems ». Journal of Vibration and Acoustics 139, no 5 (12 juin 2017). http://dx.doi.org/10.1115/1.4036501.

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Recent studies have presented first-order multiple time scale approaches for exploring amplitude-dependent plane-wave dispersion in weakly nonlinear chains and lattices characterized by cubic stiffness. These analyses have yet to assess solution stability, which requires an analysis incorporating damping. Furthermore, due to their first-order dependence, they make an implicit assumption that the cubic stiffness influences dispersion shifts to a greater degree than the quadratic stiffness, and they thus ignore quadratic shifts. This paper addresses these limitations by carrying-out higher-order, multiple scales perturbation analyses of linearly damped nonlinear monoatomic and diatomic chains. The study derives higher-order dispersion corrections informed by both quadratic and cubic stiffness and quantifies plane wave stability using evolution equations resulting from the multiple scales analysis and numerical experiments. Additionally, by reconstructing plane waves using both homogeneous and particular solutions at multiple orders, the study introduces a new interpretation of multiple scales results in which predicted waveforms are seen to exist over all space and time, constituting an invariant, multiharmonic wave of infinite extent analogous to cnoidal waves in continuous systems. Using example chains characterized by dimensionless parameters, numerical studies confirm that the spectral content of the predicted waveforms exhibits less growth/decay over time as higher-order approximations are used in defining the simulations' initial conditions. Thus, the study results suggest that the higher-order multiple scales perturbation analysis captures long-term, nonlocalized invariant plane waves, which have the potential for propagating coherent information over long distances.
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