References of "Noël, Jean-Philippe"
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See detailParameter reduction in nonlinear state-space identification of hysteresis
Esfahani, Alireza; Dreesen, Philippe; Tiels, Koen et al

in Mechanical Systems & Signal Processing (2018), 104

Recent work on black-box polynomial nonlinear state-space modeling for hysteresis identification has provided promising results, but struggles with a large number of parameters due to the use of ... [more ▼]

Recent work on black-box polynomial nonlinear state-space modeling for hysteresis identification has provided promising results, but struggles with a large number of parameters due to the use of multivariate polynomials. This drawback is tackled in the current paper by applying a decoupling approach that results in a more parsimonious representation involving univariate polynomials. This work is carried out numerically on input-output data generated by a Bouc-Wen hysteretic model and follows up on earlier work of the authors. The current article discusses the polynomial decoupling approach and explores the selection of the number of univariate polynomials with the polynomial degree. We have found that the presented decoupling approach is able to reduce the number of parameters of the full nonlinear model up to about 50%, while maintaining a comparable output error level. [less ▲]

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See detailExperimental study of isolas in nonlinear systems featuring modal interactions
Detroux, Thibaut ULiege; Noël, Jean-Philippe ULiege; Virgin, Lawrence et al

in PLoS ONE (2018), 13(3), 0194452

The objective of the present paper is to provide experimental evidence of isolated resonances in the frequency response of nonlinear mechanical systems. More specifically, this work explores the presence ... [more ▼]

The objective of the present paper is to provide experimental evidence of isolated resonances in the frequency response of nonlinear mechanical systems. More specifically, this work explores the presence of isolas, which are periodic solutions detached from the main frequency response, in the case of a nonlinear set-up consisting of two masses sliding on a horizontal guide. A careful experimental investigation of isolas is carried out using responses to swept-sine and stepped-sine excitations. The experimental findings are validated with advanced numerical simulations combining nonlinear modal analysis and bifurcation monitoring. In particular, the interactions between two nonlinear normal modes are shown to be responsible for the creation of the isolas. [less ▲]

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See detailNonlinearities of an aircraft Piccolo tube: Identification and modeling
Dossogne, Tilàn ULiege; Trillet, Pierre; Schoukens, Maarten et al

in Proceedings of the International Modal Analysis Conference (IMAC) XXXV (2018, February)

Piccolo tubes are parts of aircraft wings anti-icing system and consist of titanium pipes inserted into the internal structure of the slat. Due to differential thermal expansion, clearances between the ... [more ▼]

Piccolo tubes are parts of aircraft wings anti-icing system and consist of titanium pipes inserted into the internal structure of the slat. Due to differential thermal expansion, clearances between the tube and its support are unavoidable and cause the overall system to exhibit highly nonlinear behavior, resulting from impacts and friction. This paper addresses the identi cation and modeling of the nonlinearities present in the slat-Piccolo tube connection. The complete identi cation procedure, from nonlinearity detection and characterization to parameter estimation, is carried out based upon sine-sweep measurements. The use of several techniques, such as the acceleration surface method, enables to understand the complex dynamics of the Piccolo tube and build a reliable model of its nonlinearities. In particular, the parameters of nonsmooth nonlinear stiffness and damping mechanisms are estimated. The nonlinear model is finally validated on standard quali cation tests for airborne equipments. [less ▲]

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See detailSubspace-based identification of a distributed nonlinearity in time and frequency domains
Anastasio, Dario; Marchesiello, Stefano; Noël, Jean-Philippe ULiege et al

in Proceedings of the International Modal Analysis Conference (IMAC) XXXV (2018, February)

Nonlinear system identification has become of great interest during the last decades. However, a common and shared framework is not present yet, and the identification may be challenging, especially when ... [more ▼]

Nonlinear system identification has become of great interest during the last decades. However, a common and shared framework is not present yet, and the identification may be challenging, especially when real engineering structures are considered with strong nonlinearities. Subspace methods have proved to be effective when dealing with local nonlinearities, both in time domain (TNSI method) and in frequency domain (FNSI method). This study reports an improvement for both methods, as a first attempt to account for distributed nonlinearities, which is still an open question in the research community. A numerical beam under moderately large oscillations that exhibits geometric nonlinearity is considered. The object of the identification process is to exploit its behavior through the correct identification of the parameters that define the nonlinearity. Results show a high level of confidence between the two methods, and suggest that a more complete analysis of distributed nonlinear phenomena can be conducted based on these approaches. [less ▲]

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See detailModel updating of a wing-engine structure with nonlinear connections
Song, Mingming; Renson, Ludovic; Noël, Jean-Philippe ULiege et al

in Proceedings of the International Modal Analysis Conference (IMAC) XXXV (2018, February)

This paper investigates the performance of a Bayesian model updating approach using nonlinear normal modes (NNMs). The proposed approach is applied to a wing-engine structure tested in the laboratory. The ... [more ▼]

This paper investigates the performance of a Bayesian model updating approach using nonlinear normal modes (NNMs). The proposed approach is applied to a wing-engine structure tested in the laboratory. The structure response to a broadband input excitation is measured experimentally. The structure NNMs are then extracted from the measured data by combining a frequency-domain nonlinear subspace identification method with numerical continuation technique. An initial finite element model of the wing-engine structure is built in Matlab and its linear stiffness parameters and the coefficients of the local nonlinearities are selected as the updating parameters. The joint posterior probability distribution of the model parameters is estimated based on their prior distribution and the likelihood function which is defined as a Gaussian distribution of error function. The error function in this study is defined as the difference between model-predicted and identified NNMs at different energy levels. The calibrated model is then used to predict the structure response (NNMs and time history), taking into account model parameters uncertainties and modeling errors. The model predictions are compared with a set of experimental results that were not used in the calibration process and only considered for validation purpose. [less ▲]

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See detailSystem identification of jointed structures: Nonlinear modal testing vs. State-space model identification
Scheel, Maren; Kleyman, Gleb; Tatar, Ali et al

in Proceedings of the International Modal Analysis Conference (IMAC) XXXV (2018, February)

Two approaches for experimental identification of the nonlinear dynamical characteristics of jointed structures are investigated, (a) Nonlinear Modal Testing, (b) State-Space Model Identification. Both ... [more ▼]

Two approaches for experimental identification of the nonlinear dynamical characteristics of jointed structures are investigated, (a) Nonlinear Modal Testing, (b) State-Space Model Identification. Both require only minimal a priori knowledge of the specimen. For method (a), the definition of nonlinear modes as periodic motions is used, in its generalized formulation recently proposed for nonconservative systems. The theoretically required negative damping compensating the frictional dissipation is experimentally realized by properly controlled excitation. This permits the extraction of modal frequencies, damping ratios and vibrational deflection shapes as a function of the vibration level. For method (b), a state-space model with multivariate polynomial nonlinear terms is identified from the vibration response to a properly designed excitation signal. Both methods are applied to a structure with bolted joints. The quality of the extracted modal and state-space models, respectively, is assessed by comparing model-based predictions of the forced vibration response to reference measurements. [less ▲]

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See detailLocating nonlinearity in mechanical systems: A dynamic network perspective
Noël, Jean-Philippe ULiege; Schoukens, Maarten; Van den Hof, Paul

in Proceedings of the International Modal Analysis Conference (IMAC) XXXV (2018, February)

Though it is a crucial step for most identification methods in nonlinear structural dynamics, nonlinearity location is a sparsely addressed topic in the literature. In fact, locating nonlinearities in ... [more ▼]

Though it is a crucial step for most identification methods in nonlinear structural dynamics, nonlinearity location is a sparsely addressed topic in the literature. In fact, locating nonlinearities in mechanical systems turns out to be a challenging problem when treated nonparametrically, that is, without fitting a model. The present contribution takes a new look at this problem by exploiting some recent developments in the identification of dynamic networks, originating from the systems and control community. [less ▲]

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See detailVers l'identification non-linéaire des structures industrielles au moyen de sinus balayés
Dossogne, Tilàn ULiege; Noël, Jean-Philippe ULiege; Kerschen, Gaëtan ULiege

Poster (2017, November 16)

Les phénomènes vibratoires non-linéaires sont fréquemment rencontrés dans les structures mécaniques et aérospatiales. La division de ces structures en sous-systèmes assemblés ou l’usage de nouveaux ... [more ▼]

Les phénomènes vibratoires non-linéaires sont fréquemment rencontrés dans les structures mécaniques et aérospatiales. La division de ces structures en sous-systèmes assemblés ou l’usage de nouveaux matériaux favorisent l’apparition de mécanismes non-linéaires tels que le frottement, les impacts ou l'hystérésis. Il existe donc un besoin croissant en industrie de pouvoir détecter et identifier ces phénomènes non-linéaires sur des structures complexes et à grande échelle. L’ objectif de ce travail est d'établir une méthodologie d’identification des non-linéarités dans les structures industrielles, allant de la détection à la caractérisation et l’estimation de paramètres non-linéaires. Le processus d’identification est basé uniquement sur des mesures obtenues en sinus balayé, afin d’ obtenir une séparation naturelle des modes ainsi qu’une excitation suffisante des mécanismes non-linéaires. La première étape, la détection, permet de localiser spatialement les sources de non-linéarités dans une structure au moyen d’un indice de non-linéarité. La seconde étape, la caractérisation, offre une visualisation qualitative des comportements non-linéaires locaux en utilisant la méthode dite ASM (Acceleration Surface Method). Cette méthode repose sur l’approximation des forces de rappel non-linéaires au moyen de signaux d’accélération représentés dans l’espace d’état. La dernière étape a recours à la méthode x-ASM (eXtended Acceleration Surface Method) afin d’estimer la valeur de chaque paramètre linéaire du modèle grâce à des procédés d’optimisation couplés à des modèles éléments finis. L’ensemble de la méthodologie est validée sur un avion F-16 Fighting Falcon possédant des non-linéarités au niveau des connexions entre les ailes et la charge utile. [less ▲]

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See detailModel reduction and frequency residuals for a robust estimation of nonlinearities in subspace identification
De Filippis, Giovanni; Noël, Jean-Philippe ULiege; Kerschen, Gaëtan ULiege et al

in Mechanical Systems & Signal Processing (2017), 93

The introduction of the frequency-domain nonlinear subspace identification (FNSI) method in 2013 constitutes one in a series of recent attempts toward developing a realistic, first-generation framework ... [more ▼]

The introduction of the frequency-domain nonlinear subspace identification (FNSI) method in 2013 constitutes one in a series of recent attempts toward developing a realistic, first-generation framework applicable to complex structures. If this method showed promising capabilities when applied to academic structures, it is still confronted with a number of limitations which needs to be addressed. In particular, the removal of nonphysical poles in the identified nonlinear models is a distinct challenge. In the present paper, it is proposed as a first contribution to operate directly on the identified state-space matrices to carry out spurious pole removal. A modal-space decomposition of the state and output matrices is examined to discriminate genuine from numerical poles, prior to estimating the extended input and feedthrough matrices. The final state-space model thus contains physical information only and naturally leads to nonlinear coefficients free of spurious variations. Besides spurious variations due to nonphysical poles, vibration modes lying outside the frequency band of interest may also produce drifts of the nonlinear coefficients. The second contribution of the paper is to include residual terms, accounting for the existence of these modes. The proposed improved FNSI methodology is validated numerically and experimentally using a full-scale structure, the Morane-Saulnier Paris aircraft. [less ▲]

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See detailPolynomial state-space model decoupling for the identification of hysteretic systems
Esfahani, Alireza; Dreesen, Philippe; Tiels, Koen et al

in Proceedings of the IFAC World Congress (2017, July)

Hysteresis is a nonlinear effect that shows up in a wide variety of engineering and scientific fields. The identification of hysteretic systems from input-output data is an important but challenging ... [more ▼]

Hysteresis is a nonlinear effect that shows up in a wide variety of engineering and scientific fields. The identification of hysteretic systems from input-output data is an important but challenging question, which has been studied by using both tailored parametric white-box identification methods as by using black-box identification methods. The white-box modeling approach is by far the most common in identifying hysteretic systems, and has the advantage of resulting into an interpretable model, but it requires to be adjusted to a specific hysteresis model. A black-box approach can be used more universally, but results in models containing many parameters that cannot easily be interpreted. In the current paper, we propose a two-step identification procedure that combines the best of the two approaches.We employ the Bouc-Wen hysteretic model to generate data that is used for identification. The system is identified using a black-box polynomial nonlinear state-space identification procedure. We reduce the number of parameters in this model by applying a polynomial decoupling method that results in a more parsimonious representation. We compare the full black-box model with the decoupled model and show that the proposed method results in a comparable performance, while significantly reducing the number of parameters. [less ▲]

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See detailPolynomial nonlinear state-space modelling of vortex-induced vibrations: Black-box vs grey-box approach
Decuyper, Jan; Noël, Jean-Philippe ULiege; De Troyer, Tim et al

in Proceedings of the International Forum on Aeroelasticity and Structural Dynamics (2017, June)

The kinematics of oscillating bluff bodies in a fluid flow have been a hot research topic for decades. Most important are the potentially harmful vortex-induced vibrations (VIVs) where the structure is ... [more ▼]

The kinematics of oscillating bluff bodies in a fluid flow have been a hot research topic for decades. Most important are the potentially harmful vortex-induced vibrations (VIVs) where the structure is excited by alternating vortex shedding in its wake. Classical examples are the vibration of chimney stacks exposed to wind, pipelines on the sea-bed excited by the ocean currents or water tubes in heat exchangers. For these kind of fluid-structure interactions, typically an analytical solution cannot be found. Yet accurate predictions of the kinematics and the resulting dynamics are vital during for instance a design process, in monitoring applications or for control. Obtaining predictions with high fidelity have so far been restricted to solving the Navier-Stokes equations via computation fluid dynamic (CFD) simulations or to performing experiments. Both approaches are cumbersome and, in the case of CFD, requires a lot of computing power. These drawbacks make the current methods disadvantageous towards many intended applications where only limited time and resources are available to assess a certain risk. What is needed is an efficient and powerful model, flexible enough to span a wide domain in parameter space with a single set of coefficients. A task for which, we believe, system identifi cation can be a very powerful tool. [less ▲]

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See detailGrey-box state-space identification of nonlinear mechanical vibrations
Noël, Jean-Philippe ULiege; Schoukens, Johan

in International Journal of Control (2017)

The present paper deals with the identification of nonlinear mechanical vibrations. A grey-box, or semi-physical, nonlinear state-space representation is introduced, expressing the nonlinear basis ... [more ▼]

The present paper deals with the identification of nonlinear mechanical vibrations. A grey-box, or semi-physical, nonlinear state-space representation is introduced, expressing the nonlinear basis functions using a limited number of measured output variables. This representation assumes that the observed nonlinearities are localised in physical space, which is a generic case in mechanics. A two-step identification procedure is derived for the grey-box model parameters, integrating nonlinear subspace initialisation and weighted least-squares optimisation. The complete procedure is applied to an electrical circuit mimicking the behaviour of a single–input, single–output (SISO) nonlinear mechanical system and to a single–input, multiple–output (SIMO) geometrically nonlinear beam structure. [less ▲]

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See detailIdentification of complex nonlinearities using cubic splines with automatic discretization
Dossogne, Tilàn ULiege; Noël, Jean-Philippe ULiege; Kerschen, Gaëtan ULiege

in Proceedings of the International Modal Analysis Conference (IMAC) XXXV (2017, January)

One of the major challenges in nonlinear system identification is the selection of appropriate mathematical functions to model the observed nonlinearities. In this context, piecewise polynomials, or ... [more ▼]

One of the major challenges in nonlinear system identification is the selection of appropriate mathematical functions to model the observed nonlinearities. In this context, piecewise polynomials, or splines, offer a simple and flexible representation basis requiring limited prior knowledge. The generally-adopted discretization for splines consists in an even distribution of their control points, termed knots. While this may prove successful for simple nonlinearities, a more advanced strategy is needed for nonlinear restoring forces with strong local variations. The present paper specifically introduces a two-step methodology to select automatically the location of the knots. It proposes to derive an initial model, using nonlinear subspace identification, and incorporating cubic spline basis functions with fixed and equally-spaced abscissas. In a second step, the location of the knots is optimized iteratively by minimizing a least-squares cost function. A single-degree-of-freedom system with a discontinuous stiffness characteristic is considered as a case study. [less ▲]

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See detailNonlinear phase separation testing of an experimental wing-engine structure
Renson, Ludovic; Noël, Jean-Philippe ULiege; Barton, David et al

in Proceedings of the International Modal Analysis Conference (IMAC) XXXV (2017, January)

Modal testing of nonlinear engineering structures is currently a research area that attracts substantial attention. Recently, a nonlinear generalisation of phase separation testing has been proposed for ... [more ▼]

Modal testing of nonlinear engineering structures is currently a research area that attracts substantial attention. Recently, a nonlinear generalisation of phase separation testing has been proposed for identifying nonlinear normal modes (NNMs) based on input and output measurements. The nonlinear phase separation (NPS) method integrates identification and continuation tools to calculate multiple NNMs from broadband data. The present contribution reports the first experimental application of the NPS method. The structure of interest is a model inspired by a wing with two engines connected by means of nonlinear pylons with softening-hardening stiffness characteristics. The frequency-energy dependences of four NNMs in the 0-100 Hz range are estimated, including modal interactions. NNMs identified using the NPS method are also compared to free-decay testing results. [less ▲]

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See detailBayesian FE model updating using nonlinear normal modes: Application to a cantilever beam
Song, Mingming; Renson, Ludovic; Noël, Jean-Philippe ULiege et al

in Proceedings of the International Modal Analysis Conference (IMAC) XXXV (2017, January)

This paper investigates the performance of a probabilistic finite element (FE) model updating approach using the Bayesian inference and nonlinear normal mode (NNM) error functions. The considered beam is ... [more ▼]

This paper investigates the performance of a probabilistic finite element (FE) model updating approach using the Bayesian inference and nonlinear normal mode (NNM) error functions. The considered beam is the European COST Action F3 benchmark and its response in this study is simulated when subjected to a broadband excitation. The simulated response is then contaminated with different levels of Gaussian white noise to represent noisy measurements. The NNMs of the beam are identified from the noisy data by integrating a nonlinear subspace identification method and numerical continuation in a phase separation approach. An initial FE model of the beam is created in Matlab and its parameters are probabilistically updated. The considered updating parameters are the Young’s modulus of the main beam and coefficients of the local geometric nonlinearity. In the proposed FE model updating approach, error functions are defined as the difference between model-predicted and identified NNMs at different energy levels. Posterior probability distributions of the updating parameters are estimated for different levels of measurement noise. The error function is assumed to have a Gaussian distribution. Performance of the updating results are studied for two cases, namely (1) when the error mean is assumed to be zero and the error covariance is known, and (2) when both the error mean and covariance are updated. [less ▲]

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See detailNonlinear system identification in structural dynamics: 10 more years of progress
Noël, Jean-Philippe ULiege; Kerschen, Gaëtan ULiege

in Mechanical Systems & Signal Processing (2017), 83

Nonlinear system identification is a vast research field, today attracting a great deal of attention in the structural dynamics community. Ten years ago, in an MSSP paper reviewing the progress achieved ... [more ▼]

Nonlinear system identification is a vast research field, today attracting a great deal of attention in the structural dynamics community. Ten years ago, in an MSSP paper reviewing the progress achieved until then, it was concluded that the identification of simple continuous structures with localised nonlinearities was within reach. The past decade witnessed a shift in emphasis, accommodating the growing industrial need for a first generation of tools capable of addressing complex nonlinearities in larger-scale structures. The objective of the present paper is to survey the key developments which arose in the field since 2006, and to illustrate state-of-the-art techniques using a real-world satellite structure. Finally, a broader perspective to nonlinear system identification is provided by discussing the central role played by experimental models in the design cycle of engineering structures. [less ▲]

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See detailA nonlinear state-space approach to hysteresis identification
Noël, Jean-Philippe ULiege; Esfahani, Alireza; Kerschen, Gaëtan ULiege et al

in Mechanical Systems & Signal Processing (2017), 84

Most studies tackling hysteresis identification in the technical literature follow white-box approaches, i.e. they rely on the assumption that measured data obey a specific hysteretic model. Such an ... [more ▼]

Most studies tackling hysteresis identification in the technical literature follow white-box approaches, i.e. they rely on the assumption that measured data obey a specific hysteretic model. Such an assumption may be a hard requirement to handle in real applications, since hysteresis is a highly individualistic nonlinear behaviour. The present paper adopts a black-box approach based on nonlinear state-space models to identify hysteresis dynamics. This approach is shown to provide a general framework to hysteresis identification, featuring flexibility and parsimony of representation. Nonlinear model terms are constructed as a multivariate polynomial in the state variables, and parameter estimation is performed by minimising weighted least-squares cost functions. Technical issues, including the selection of the model order and the polynomial degree, are discussed, and model validation is achieved in both broadband and sine conditions. The study is carried out numerically by exploiting synthetic data generated via the Bouc-Wen equations. [less ▲]

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See detailA new, challenging benchmark for nonlinear system identification
Tiso, Paolo; Noël, Jean-Philippe ULiege

in Mechanical Systems & Signal Processing (2017), 84

The progress accomplished during the past decade in nonlinear system identi fication in structural dynamics is considerable. The objective of the present paper is to consolidate this progress by ... [more ▼]

The progress accomplished during the past decade in nonlinear system identi fication in structural dynamics is considerable. The objective of the present paper is to consolidate this progress by challenging the community through a new benchmark structure exhibiting complex nonlinear dynamics. The proposed structure consists of two o ffset cantilevered beams connected by a highly flexible element. For increasing forcing amplitudes, the system sequentially features linear behaviour, localised nonlinearity associated with the buckling of the connecting element, and distributed nonlinearity resulting from large elastic deformations across the structure. A finite element-based code with time integration capabilities is made available at http://sem.org/TDIV-Nonlin.asp. This code permits the numerical simulation of the benchmark dynamics in response to arbitrary excitation signals. [less ▲]

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See detailAnalysis of the Nonlinear Dynamics of an F-16 Aircraft Using the NI2D Toolbox
Detroux, Thibaut ULiege; Dossogne, Tilàn ULiege; Masset, Luc ULiege et al

Conference (2016, October)

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See detailNonlinear vibration analysis of the SmallSat spacecraft: From identification to design
Detroux, Thibaut ULiege; Noël, Jean-Philippe ULiege; Masset, Luc ULiege et al

Conference (2016, September)

The objective of the present contribution is to introduce nonlinear experimental and numerical tools and methods applicable to real-life structures. The study is illustrated using the SmallSat spacecraft ... [more ▼]

The objective of the present contribution is to introduce nonlinear experimental and numerical tools and methods applicable to real-life structures. The study is illustrated using the SmallSat spacecraft developed by Airbus Defence and Space, which possesses several localized nonlinearities. The computation of nonlinear normal modes and bifurcations reveals that the satellite possesses complex dynamics including modal interactions, quasiperiodic oscillations and isolated resonances. [less ▲]

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