Letteratura scientifica selezionata sul tema "Generalised Maxwell Model"
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Articoli di riviste sul tema "Generalised Maxwell Model"
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Karner, Timi, Rok Belšak e Janez Gotlih. "Using a Fully Fractional Generalised Maxwell Model for Describing the Time Dependent Sinusoidal Creep of a Dielectric Elastomer Actuator". Fractal and Fractional 6, n. 12 (4 dicembre 2022): 720. http://dx.doi.org/10.3390/fractalfract6120720.
Testo completoAbstract (sommario):
Actuators made of dielectric elastomers are used in soft robotics for a variety of applications. However, due to their mechanical properties, they exhibit viscoelastic behaviour, especially in the initial phase of their performance, which can be observed in the first cycles of dynamic excitation. A fully fractional generalised Maxwell model was derived and used for the first time to capture the viscoelastic effect of dielectric elastomer actuators. The Laplace transform was used to derive the fully fractional generalised Maxwell model. The Laplace transform has proven to be very useful and practical in deriving fractional viscoelastic constitutive models. Using the global optimisation procedure called Pattern Search, the optimal parameters, as well as the number of branches of the fully fractional generalised Maxwell model, were derived from the experimental results. For the fully fractional generalised Maxwell model, the optimal number of branches was determined considering the derivation order of each element of the branch. The derived model can readily be implemented in the simulation of a dielectric elastomer actuator control, and can also easily be used for different viscoelastic materials.
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Fabris, Júlio C. "Cosmological model from generalised Maxwell-Einstein system in higher dimensions". Physics Letters B 267, n. 1 (settembre 1991): 30–32. http://dx.doi.org/10.1016/0370-2693(91)90519-v.
Testo completo
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Zhao, Yanqing, Yuanbao Ni e Weiqiao Zeng. "A consistent approach for characterising asphalt concrete based on generalised Maxwell or Kelvin model". Road Materials and Pavement Design 15, n. 3 (26 febbraio 2014): 674–90. http://dx.doi.org/10.1080/14680629.2014.889030.
Testo completo
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Liu, Zizhen, e Lynne Bilston. "On the viscoelastic character of liver tissue: experiments and modelling of the linear behaviour". Biorheology: The Official Journal of the International Society of Biorheology 37, n. 3 (maggio 2000): 191–201. http://dx.doi.org/10.1177/0006355x2000037003002.
Testo completoAbstract (sommario):
This paper presents the results of recent investigations into the viscoelastic character of liver tissue, especially the linear response. The linear domain of liver tissue has been determined by a strain sweep oscillation test. The fluid‐like viscoelastic behaviour of liver tissue was confirmed by stress relaxation experiments. To demonstrate the consistency and quality of the experimental data, the relaxation spectrum was used to reconstruct the relaxation modulus, as well as the storage and loss moduli. The generalised Maxwell model was successfully employed to model the mechanical behaviour in the linear viscoelastic domain.
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Long, Le Dinh, Bahman Moradi, Omid Nikan, Zakieh Avazzadeh e António M. Lopes. "Numerical Approximation of the Fractional Rayleigh–Stokes Problem Arising in a Generalised Maxwell Fluid". Fractal and Fractional 6, n. 7 (2 luglio 2022): 377. http://dx.doi.org/10.3390/fractalfract6070377.
Testo completoAbstract (sommario):
This paper presents a numerical technique to approximate the Rayleigh–Stokes model for a generalised Maxwell fluid formulated in the Riemann–Liouville sense. The proposed method consists of two stages. First, the time discretization of the problem is accomplished by using the finite difference. Second, the space discretization is obtained by means of the predictor–corrector method. The unconditional stability result and convergence analysis are analysed theoretically. Numerical examples are provided to verify the feasibility and accuracy of the proposed method.
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Yang, X. S. "Nonlinear viscoelastic compaction in sedimentary basins". Nonlinear Processes in Geophysics 7, n. 1/2 (30 giugno 2000): 1–8. http://dx.doi.org/10.5194/npg-7-1-2000.
Testo completoAbstract (sommario):
Abstract. In the mathematical modelling of sediment compaction and porous media flow, the rheological behaviour of sediments is typically modelled in terms of a nonlinear relationship between effective pressure pe and porosity Φ, that is pe = pe (Φ). The compaction law is essentially a poroelastic one. However, viscous compaction due to pressure solution becomes important at larger depths and causes this relationship to become more akin to a viscous rheology. A generalised viscoelastic compaction model of Maxwell type is formulated, and different styles of nonlinear behaviour are asymptotically analysed and compared in this paper.
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Schiffmann, Kirsten Ingolf. "Nanoindentation creep and stress relaxation tests of polycarbonate: Analysis of viscoelastic properties by different rheological models". International Journal of Materials Research 97, n. 9 (1 settembre 2006): 1199–211. http://dx.doi.org/10.1515/ijmr-2006-0189.
Testo completoAbstract (sommario):
Abstract Feedback-controlled nanoindentation with a Berkovich diamond tip has been used to perform creep and stress relaxation tests on polycarbonate at room temperature for a wide range of loads (10 – 30000 μN) and indentation depths (30 – 3000 nm). The creep compliance J(t) and relaxation modulus G(t) have been calculated from experimental data as a function of time in the range t = 0.1 – 100 (1000) s. The data are analysed by different rheological models which are compared: (1) the Burgers model, (2) the generalised Maxwell/generalised Kelvin model, and two empirical approaches: (3) a logarithmic model, and (4) a power law model. The Burgers model gives a poor description of the material behaviour since it assumes a steady-state flow of material which is not observed in the experimental time range. The generalised models yield a set of discrete relaxation- and retardation time constants. It is shown that these time constants do not correlate with specific molecular moving processes in the polymer, but are only one of several possible parameterisations of the creep and relaxation curves. Numerical differentiation of G(t) and J(t) shows that polycarbonate has continuous relaxation- and retardation time spectra, respectively, and the dynamic viscosity η(t) of the material increases linearly with time. The behaviour of polycarbonate is best represented by the empirical power law model, which allows optimum fit of creep/relaxation curves, relaxation and retardation time spectra and time-dependent viscosity.
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Naveena Kumara, A., Shreyas Punacha e Md Sabir Ali. "Lyapunov exponents and phase structure of Lifshitz and hyperscaling violating black holes". Journal of Cosmology and Astroparticle Physics 2024, n. 07 (1 luglio 2024): 061. http://dx.doi.org/10.1088/1475-7516/2024/07/061.
Testo completoAbstract (sommario):
Abstract We study the phase structure of Lifshitz and hyperscaling violating (HSV) black holes using Lyapunov exponents. For describing hyperscaling violating system, we chose a particular gravity model constructed from generalized Einstein-Maxwell-Dilaton action which includes the Lifshitz cases at appropriate limits. We study the relationship between Lyapunov exponents and black hole phase transitions considering both the timelike and null geodesics. We observe that, the black hole phase transiton properties are reflected in Lyapunov exponent where its multiple branches correspond to the distinct phases of the black hole. The discontinuos change of the Lyapunov exponent during the phase transition serve as an order parameter with critical exponent 1/2 near the critical point. Our numerical study reveals that the correlation between the Lyapunov exponent and black hole thermodynamic properties can be generalised beyond the AdS spacetime. We find that it is independent of the HSV parameter as well as the Lifshitz exponent.
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Gerritzen, Johannes, Michael Müller-Pabel, Jonas Müller, Benjamin Gröger, Niklas Lorenz, Christian Hopmann e Maik Gude. "Development of a High-Fidelity Framework to Describe the Process-Dependent Viscoelasticity of a Fast-Curing Epoxy Matrix Resin including Testing, Modelling, Calibration and Validation". Polymers 14, n. 17 (2 settembre 2022): 3647. http://dx.doi.org/10.3390/polym14173647.
Testo completoAbstract (sommario):
Fast-curing epoxy resins enable substantial reduction of cycle times during production of thermoset polymer matrix composites. Due to the snap-cure behaviour, both characterisation and processing of these resins are associated with high complexity which motivates the development of a high-fidelity framework for the prediction of the process-dependent behaviour ranging from experiment to model validation. In order to determine influence of time, temperature, and degree of cure, a multitude of rheometer and dynamic mechanical analysis experiments are conducted and evaluated. Building on the experimental results, a material model based on a generalised Maxwell model is developed. It is calibrated on the results obtained in the tests and shown to describe the material’s behaviour with high accuracy under all investigated conditions. The model’s predictive capabilities are further tested by applying it to a dynamic mechanical analysis, exposing the model to previously unknown loading and temperature conditions. It is demonstrated that the model is capable of predicting such changing boundary conditions with high accuracy.
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Parodi, Pietro, e Peter Watson. "PROPERTY GRAPHS – A STATISTICAL MODEL FOR FIRE AND EXPLOSION LOSSES BASED ON GRAPH THEORY". ASTIN Bulletin 49, n. 2 (27 marzo 2019): 263–97. http://dx.doi.org/10.1017/asb.2019.4.
Testo completoAbstract (sommario):
AbstractIt is rare that the severity loss distribution for a specific line of business can be derived from first principles. One such example is the use of generalised Pareto distribution for losses above a large threshold (or more accurately: asymptotically), which is dictated by extreme value theory. Most popular distributions, such as the lognormal distribution or the Maxwell-Boltzmann-Bose-Einstein-Fermi-Dirac (MBBEFD), are convenient heuristics with no underlying theory to back them. This paper presents a way to derive a severity distribution for property losses based on modelling a property as a weighted graph, that is, a collection of nodes and weighted arcs connecting these nodes. Each node v (to which a value can also be assigned) corresponds to a room or a unit of the property where a fire can occur, while an arc (v, v′; p) between vertices v and v′ signals that the probability of the fire propagating from v to v′ is p. The paper presents two simple models for fire propagation (the random graph approach and the random time approach) and a model for explosion risk that allow one to calculate the loss distribution for a given property from first principles. The MBBEFD model is shown to be a good approximation for the simulated distribution of losses based on property graphs for both the random graph and the random time approach.
Tesi sul tema "Generalised Maxwell Model"
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Lu, Kang. "The Application of Generalised Maxwell-Stefan Equations to Protein Gels". Thesis, University of Canterbury. Chemical and Process Engineering, 2007. http://hdl.handle.net/10092/1236.
Testo completoAbstract (sommario):
The removal of milk fouling deposits often requires the diffusion of electrolyte solutions such as sodium hydroxide through a gel. Very often more than one single anion and one single cation are involved and thus the modelling of such diffusion requires a multicomponent description. Diffusion of electrolyte solutions through gels can be modelled using the Maxwell-Stefan equation. The driving forces for diffusion are the chemical potential gradients of ionic species and the diffusion potential, i.e., the electrostatic potential induced by diffusion of the ions. A model based on the Maxwell-Stefan equation was applied to electrolyte solutions and electrolyte solutions with a gel. When modelling the diffusion of electrolyte solutions, the resulting equations were found to be a partial differential algebraic equation system with a differentiation index of two. The identification of this characteristic of the system enabled a solution method using the method of lines to be developed. When modelling the diffusion of electrolyte solutions through a gel an explicit expression for diffusion potential was developed and hence the diffusion equations were solved. Numerical solutions were presented for a number of case studies and comparisons were made with solutions from literature and between different electrolyte systems. It was found that the results of diffusion of electrolytes were in good agreement with those of experiments and literature. In the case of diffusion of electrolytes through a gel, swelling of the gel was predicted. The model can be improved by adding thermodynamic factors and can be easily extended to multiple ion systems.
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Goddard, Chris. "Rheological chaos and elastic turbulence in a generalised Maxwell model for viscoelastic fluid flow". Thesis, University of Surrey, 2008. http://epubs.surrey.ac.uk/2773/.
Testo completoAbstract (sommario):
This work presents a new extension to a generalised nonlinear Maxwell model for the theoty of viscoelastic material flow. Nonlinear terms within this constitutive model are used to replicate many experimental phenomena such as shear-thickening/thinning, shear banding and dynamic stress responses found in complex materials such as polymers, Micelles, colloidal dispersions and even granular media. Numerical simulations of the stress tensor under spatially homogeneous plane Couette flow reveal a range of solutions from steady state to chaotic, chosen in part by the strength of nonlinear terms. Bifurcation and stability analysis reveal the onset of chaotic flow and are used to study the various transitions to chaos. A detailed phase space diagram is produced to categorise different dynamical regimes by determining the Lyapunov exponent under variation of two main model parameters. The route to chaos is identified primarily as a Hopf bifurcation.
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Katicha, Samer. "Analysis of Hot Mix Asphalt (HMA) Linear Viscoelastic and Bimodular Properties Using Uniaxial Compression and Indirect Tension (IDT) Tests". Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/30036.
Testo completoAbstract (sommario):
The major Hot-Mix Asphalt (HMA) input for mechanistic-empirical (M-E) flexible pavement design is the dynamic complex modulus obtained from either the uniaxial or triaxial compressive dynamic modulus test. Furthermore, as part of the performance-based mix design process, the triaxial dynamic modulus has been selected to predict rutting and fatigue cracking, and the Indirect Tension (IDT) creep compliance test to predict low-temperature thermal cracking.
The creep compliance and dynamic modulus are measured responses (viscoelastic functions) of viscoelastic materials under transient and cyclic loading, respectively. Under the assumptions of linearity, linear viscoelastic functions are equivalent. Moreover, these properties should be the same whether they are obtained from a uniaxial compressive or IDT test.
For this dissertation, we tested the applicability of linear viscoelastic (LVE) theory to HMA mixes and determined whether HMA need to be modeled as a bimodular material to analyze IDT creep compliance test results. The need to model HMA as a bimodular material is a result of a number of studies that suggest that HMA tensile and compressive properties are different.
A testing program was developed to experimentally measure the uniaxial compression, and IDT creep compliance, and the uniaxial compression dynamic modulus for different HMA mixes. The uniaxial compressive creep compliance and dynamic modulus master curves are constructed and the shift factors obtained from each test are compared. Interconversion between the creep compliance and dynamic modulus experimental results confirm the applicability of LVE theory for the HMA mixes investigated. Based on the applicability of LVE theory, a methodology to determine HMA LVE properties from the combined creep compliance and dynamic modulus test results was developed.
As a practical application that is relevant to the M-E flexible pavement design procedure, LVE theory was used and compared to proposed approximate methods to perform the conversion of testing frequency to loading time. Specifically, dynamic modulus results were converted to relaxation modulus, creep compliance, and resilient modulus.
Finally, the HMA IDT creep compliance test results at low and intermediate temperature (<20oC) were successfully analyzed using a HMA bimodular material model based on the Ambartsumyan model. The difference between the compressive modulus and the modulus calculated from the IDT test using Hondrosâ stress distribution is calculated. In addition, a method to determine the compressive-to-tensile modulus ratio using uniaxial compressive and IDT test results is illustrated for one of the tested HMA mixes.Ph. D.
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Pistenon, Nicolas. "Découvrir la loi de comportement de matériaux viscoélastiques non linéaires par réseaux de neurones à base physique et données expérimentales". Electronic Thesis or Diss., Université Paris sciences et lettres, 2024. http://www.theses.fr/2024UPSLM044.
Testo completoAbstract (sommario):
Les méthodes d'apprentissage automatique basées sur les réseaux de neurones offrent de nouvelles perspectives pour la modélisation du comportement mécanique des matériaux. Grâce à leur capacité à servir d'interpolateurs universels de fonctions, ces réseaux sont capables de capturer une grande variété de comportements complexes. Cependant, leur mise en œuvre requiert des ensembles de données volumineux, souvent difficilement accessibles par des moyens expérimentaux. Afin de pallier cette limitation, ce manuscrit introduit différents biais physiques permettant de modéliser le comportement mécanique de matériau, et plus spécifiquement le comportement viscoélastique non linéaire, à partir de données expérimentales restreintes.Les deux principes fondamentaux de la thermodynamique constituent un cadre contraignant pour la formulation de lois de comportement. Il permet de réduire le nombre de données nécessaires à l'entraînement des modèles, tout en renforçant leur robustesse face aux erreurs de mesure.Les réseaux de neurones récurrents, quant à eux, sont particulièrement bien adaptés pour modéliser des comportements dépendant de l'histoire du chargement. Leurs mémoires cachées offrent une analogie intéressante avec les variables internes introduites par le principe de l'état local en mécanique. Cependant, ces réseaux posent des défis en matière d'entraînement et de généralisation. Pour surmonter ces difficultés, un modèle de réseau de neurones à encodage mécanique est proposé. Ce modèle tire parti des variables internes d'un modèle de viscoélasticité linéaire pour encoder l'histoire du matériau, ce qui s'avère suffisant pour modéliser le comportement mécanique non linéaire du matériau.Un des défis majeurs de la modélisation en trois dimensions à partir de données expérimentales réside dans la prise en compte des symétries matérielles pour éviter des essais redondants. Dans le cas des matériaux isotropes, une méthode d'augmentation de données par rotation aléatoire des essais, combinée à un apprentissage par transfert latéral, permet de développer une loi de comportement 3D en utilisant seulement deux types d'essais uniaxiaux. Une formulation thermodynamique respectant intrinsèquement l'isotropie du matériau est proposée, bien que des défis d'entraînement restent à surmonter pour optimiser cette approcheThe application of machine learning techniques based on neural networks provides novel insights into the modelling of the mechanical behaviour of materials. These networks are capable of capturing a wide variety of complex behaviours due to their ability to act as universal function approximators. However, the deployment of these techniques requires large datasets, which are often difficult to obtain experimentally. This manuscript introduces various physical biases that enable the modelling of mechanical behaviour, specifically non-linear viscoelastic behaviour, using limited experimental data, thereby addressing this limitation.The two fundamental principles of thermodynamics provide a robust framework for constraining the formulation of constitutive laws. This approach reduces the quantity of data required for model training, while simultaneously improving the models' resilience to measurement errors.Recurrent neural networks, on the other hand, are particularly well-suited for modelling behaviour that depends on the loading history. Their hidden memories mirror the internal variables introduced in mechanics by the local state principle. However, these networks present challenges in terms of training and generalisation. To overcome these difficulties, a neural network model with mechanical encoding is proposed. This model employs the internal variables of a linear viscoelasticity model to encode the material's history, which proves to be sufficient for modelling its non-linear mechanical behaviour.One of the most significant challenges in three-dimensional modelling from experimental data is the incorporation of material symmetries in order to avoid the need for superfluous testing. For isotropic materials, a method of increasing the data set by randomly rotating the tests, combined with lateral transfer learning, enables the development of a three-dimensional constitutive law using only two types of uniaxial test. A thermodynamically consistent formulation that inherently preserves the material's isotropy is proposed; however, challenges related to training remain to be addressed in order to optimise this approach
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Jaboviste, Kévin. "Caractérisation expérimentale et modélisation de solutions amortissantes pour la réduction des transferts vibratoires et la stabilisation de systèmes embarqués". Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD068/document.
Testo completoAbstract (sommario):
Les travaux effectués durant cette thèse portent sur l’étude du comportement mécanique dynamique de solutions amortissantes passives utilisées pour la réduction des niveaux vibratoires et la stabilisation des systèmes optroniques embarqués au sein de l’entreprise Thales LAS France. Ces solutions intègrent des matériaux élastomères au fort pouvoir dissipatif dont le comportement doit être parfaitement maîtrisé pour un bon dimensionnement de l’isolation vibratoire, et ce malgré leur dépendance à la température et à la fréquence. L’objectif général est d’améliorer la connaissance du comportement de ces matériaux, leur caractérisation, leur prise en compte dans les simulations numériques afin d’améliorer les pratiques employées dans les bureaux d’études qui conçoivent les structures accueillant ces systèmes.Dans ce cadre, les travaux présentés portent tout d’abord sur la caractérisation, la modélisation et l’identification du comportement viscoélastique des élastomères employés dans des amortisseurs de Thales LAS France. Un modèle de type Maxwell généralisé (GMM) est utilisé pour décrire ce comportement, et est introduit dans un modèle éléments finis de l’amortisseur afin d’obtenir une représentation physique satisfaisante de son comportement mécanique dynamique. Le problème est réécrit sous la forme d’une représentation d’état originale qui est associée à une stratégie de réduction de modèle pour réduire les temps de calcul. Différentes simulations sont alors réalisées pour illustrer le potentiel de l’approche proposée, analyse modale complexe, réponse fréquentielle et réponse temporelle. La température ayant une influence primordiale sur le comportement mécanique des élastomères, un modèle matériau thermomécanique spécifique est proposé en identifiant l’évolution en température de paramètres du GMM, et une analyse de robustesse portant sur la capacité de dissipation de l’amortisseur témoin en présence de méconnaissances sur cette variable est réalisée en se basant sur la théorie Info-Gap.L’analyse d’une campagne d’essais a permis de constater l’apparition d’un assouplissement de la structure sous de fortes sollicitations, laissant augurer la présence de non-linéarités. Un autre aspect abordé durant cette thèse porte ainsi sur la caractérisation, la modélisation et l’identification des phénomènes non-linéaires pouvant impacter le comportement dynamique de l’amortisseur. Deux sources ont été mises en évidence : une non-linéarité matérielle liée à la dépendance des caractéristiques mécaniques des élastomères au taux de déformation (effet Payne), et une non-linéarité de type contact liée à la présence de butées. Ces comportements ont été implémentés dans une représentation réduite de l’amortisseur afin d’expliquer les phénomènes non-linéaires observés expérimentalement au cours des campagnes de qualification du produit.Enfin, la dernière partie de ces travaux de thèse porte sur la conception d’un réseau d’absorbeurs à masses accordées (MTMD) afin de réduire le niveau vibratoire d’une pièce structurale supportant les systèmes optiques. Après une formulation du problème éléments finis, une procédure d’optimisation des paramètres du MTMD est mise en œuvre et une analyse de robustesse de la solution optimale en présence d’incertitudes sur la fréquence propre à contrôler est effectuée. Cette étude est menée pour différents jeux de paramètres et une méthode d’optimisation robuste est proposée en combinant la procédure d’optimisation et la théorie Info-Gap. Pour finir, une maquette du système étudié est réalisée ainsi qu’une version simplifiée de son MTMD associé afin de mettre à l’épreuve les règles d’accordage issues des études numériques grâce à une série d’essais vibratoiresThe work carried out during this thesis deals with the study of the dynamic mechanical behavior of passive damping solutions used for the reduction of vibration levels and the stabilization of embedded optronic systems within Thales LAS France company. These solutions integrate elastomer materials with high dissipative power, whose behavior must be perfectly controlled for a good mechanical dimensioning of vibration isolation, despite their dependence on temperature and frequency. The general objective is to improve the knowledge of these material behavior, the characterization techniques, and the method taking into account this behavior in the numerical simulations in order to improve the practices used in the engineering department that design the structures hosting these systems.In this context, the work presented first focuses on the characterization, the modeling and the identification of the viscoelastic behavior of elastomers used in Thales LAS France damping devices. A Generalized Maxwell Model (GMM) is used to describe this behavior, and is introduced into a finite element model of the damper to obtain a satisfactory physical representation of its dynamic mechanical behavior. The problem is rewritten as an original state space representation that is associated with a model reduction strategy to reduce computation times. Various simulations are moreover performed to illustrate the potential of the proposed approach, such as complex modal analysis, frequency response and temporal response. Since temperature has a major influence on the mechanical behavior of elastomers, a specific thermomechanical material model is proposed by identifying the temperature evolution of GMM parameters, and a robustness analysis on the dissipation ability of the damper in the presence of a lack-of-knowledge on this variable is carried out based on the Info-Gap theory.Experimental test results showed the appearance of a softening of the structure under heavy load, suggesting the presence of non-linearities. Another aspect of this thesis deals with the characterization, the modeling and the identification of non-linear phenomena that can impact the dynamic behavior of the damper. Two sources have been highlighted: a material non-linearity related to the dependence of the mechanical characteristics of the elastomers to the rate of deformation (Payne effect), and a contact non-linearity related to the presence of mechanical stops. These behaviors were implemented in a reduced representation of the damper to explain the nonlinear phenomena observed experimentally during the damping device qualification campaigns.Finally, the last part of this thesis deals with the design of a network of tuned mass absorbers (MTMD) in order to reduce the vibratory level of a structural part supporting optical systems. After a formulation of the finite element problem, a procedure for optimizing the parameters of the MTMD is implemented and a robustness analysis of the optimal solution in the presence of uncertainties on the specific eigenfrequency to be controlled is performed. This study is carried out for different sets of parameters and a robust design optimization method is proposed by combining the optimization procedure and the Info-Gap theory. Finally, a model of the studied system is realized as well as a simplified version of its associated MTMD in order to test the tuning rules resulting from numerical studies thanks to a series of experimental tests
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Babahosseini, Hesam. "Single Cell Biomechanical Phenotyping using Microfluidics and Nanotechnology". Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/64502.
Testo completoAbstract (sommario):
Cancer progression is accompanied with alterations in the cell biomechanical phenotype, including changes in cell structure, morphology, and responses to microenvironmental stress. These alterations result in an increased deformability of transformed cells and reduced resistance to mechanical stimuli, enabling motility and invasion. Therefore, single cell biomechanical properties could be served as a powerful label-free biomarker for effective characterization and early detection of single cancer cells. Advances and innovations in microsystems and nanotechnology have facilitated interrogation of the biomechanical properties of single cells to predict their tumorigenicity, metastatic potential, and health state.
This dissertation utilized Atomic Force Microscopy (AFM) for the cell biomechanical phenotyping for cancer diagnosis and early detection, efficacy screening of potential chemotherapeutic agents, and also cancer stem-like/tumor initiating cells (CSC/TICs) characterization as the critical topics received intensive attention in the search for effective cancer treatment. Our findings demonstrated the capability of exogenous sphingosine to revert the aberrant biomechanics of aggressive cells and showed a unique, mechanically homogeneous, and extremely soft characteristic of CSC/TICs, suitable for their targeted isolation. To make full use of cell biomechanical cues, this dissertation also considered the application of nonlinear viscoelastic models such as Fractional Zener and Generalized Maxwell models for the naturally complex, heterogeneous, and nonlinear structure of living cells.
The emerging need for a high-throughput clinically relevant alternative for evaluating biomechanics of individual cells led us to the development of a microfluidic system. Therefore, a high-throughput, label-free, automated microfluidic chip was developed to investigate the biophysical (biomechanical-bioelectrical) markers of normal and malignant cells.
Most importantly, this dissertation also explored the biomechanical response of cells upon a dynamic loading instead of a typical transient stress. Notably, metastatic and non-metastatic cells subjected to a pulsed stress regimen exerted by AFM exhibited distinct biomechanical responses. While non-metastatic cells showed an increase in their resistance against deformation and resulted in strain-stiffening behavior, metastatic cells responded by losing their resistance and yielded slight strain-softening. Ultimately, a second generation microfluidic chip called an iterative mechanical characteristics (iMECH) analyzer consisting of a series of constriction channels for simulating the dynamic stress paradigm was developed which could reproduce the same stiffening/softening trends of non-metastatic and metastatic cells, respectively. Therefore, for the first time, the use of dynamic loading paradigm to evaluate cell biomechanical responses was used as a new signature to predict malignancy or normalcy at a single-cell level with a high (~95%) confidence level.Ph. D.
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Ahmadi, Aras. "Modélisation de l'absorption réactive multiconstituant : application au traitement des gaz acides par des solvants aux alcanolamines". Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0077/document.
Testo completoAbstract (sommario):
Les gaz issus de la combustion des énergies fossiles dans les centrales électriques contiennent une grande variété de polluants tels que les gaz-acides et ne peuvent être rejetés directement dans l'atmosphère. Ces polluants gazeux doivent être traités par des méthodes de captage en post combustion dans des colonnes d'absorption utilisant des solvants chimiques. L'objectif est donc de concevoir une unité d'élimination sélective des gaz-acides tels que CO2, H2S et COS en utilisant des solvants de la famille des alcanolamines. Cette thèse développe dans un premier temps, un modèle de non-équilibre, adapté aux systèmes multiconstituants électrolytiques et réactifs, pour la représentation des colonnes d'absorption réactive. Le modèle comporte des modules pour représenter la thermodynamique en espèces vraies (espèces ioniques et moléculaires), le transfert simultané de masse et de chaleur, et les réactions chimiques. Les équations généralisées de Maxwell-Stefan sont utilisées pour quantifier les interactions multiconstituants lors de la diffusion. Le schéma réactionnel est intégralement pris en compte dans la phase liquide, et les réactions chimiques peuvent être cinétiquement contrôlées ou à l'équilibre chimique instantané. La séparation réactive en régime permanent est ainsi simulée avec une description rigoureuse des phénomènes de réaction-diffusion dans les films diffusionnels. Dans un deuxième temps, une installation pilote de captage du CO2 par une solution aqueuse de diéthanolamine est mise en fluvre pour la validation expérimentale du modèle. La diéthanolamine a une forte réactivité vis-à-vis du CO2; ceci engendre un profil important de concentration du soluté dans la colonne. Le pilote est dédié à la validation de modèle, il est donc équipé de plusieurs unités d'échantillonnage gaz et liquide à différentes hauteurs de garnissage. Les profils longitudinaux de la concentration du CO2 en gaz et en liquide, de l'humidité absolue et de la température liquide peuvent être établis expérimentalement et être comparés avec ceux provenant de la simulation. L'outil de simulation validé devient alors un outil de prédiction de l'efficacité des unités réelles de captage par l'absorption réactiveThe exhaust gases coming from the combustion of fossil fuels in power plants contain a wide variety of pollutants such as acid gases and can not be discharged directly into the atmosphere. These gaseous pollutants must be treated by postcombustion capture methods in absorption columns using chemical solvents. The objective is then to design a selective removal unit of acid-gases such as CO2, H2S and COS by using solvents of the alkanolamine family. This thesis develops as the first step, a non-equilibrium model, adapted to multicomponent electrolytic and reactive systems, for the representation of reactive absorption columns. The model includes modules to represent the thermodynamics on the basis of true species (ionic and molecular species), the simultaneous heat and mass transfer, and the chemical reactions. The generalized equations of Maxwell-Stefan are used to take into account the multicomponent interactions during diffusion. The reaction scheme is fully included in the liquid phase, and the chemical reactions can be kinetically controlled or at instantaneous equilibrium. The reactive separation at steady-state conditions is then simulated with a rigorous description of the reaction-diffusion phenomena in diffusional films. In the second step, a pilot plant of CO2 capture with an aqueous solution of diethanolamine is implemented for experimental validation of the model. Diethanolamine has high reactivity with respect to CO2; this generates an important concentration profile of solute in the column. The pilot plant is dedicated to model validation; it is equipped with several gas and liquid sampling units at different heights of packing. The longitudinal profiles of the gas and liquid CO2 concentration, the absolute humidity and the liquid temperature can be established experimentally and compared with those from the simulation. The validated simulation tool then becomes a tool to predict the effectiveness of real capture units by reactive absorption
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Zou, Yaotian. "Over- and Under-dispersed Crash Data: Comparing the Conway-Maxwell-Poisson and Double-Poisson Distributions". Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11521.
Testo completoAbstract (sommario):
In traffic safety analysis, a large number of distributions have been proposed to analyze motor vehicle crashes. Among those distributions, the traditional Poisson and Negative Binomial (NB) distributions have been the most commonly used. Although the Poisson and NB models possess desirable statistical properties, their application on modeling motor vehicle crashes are associated with limitations. In practice, traffic crash data are often over-dispersed. On rare occasions, they have shown to be under-dispersed. The over-dispersed and under-dispersed data can lead to the inconsistent standard errors of parameter estimates using the traditional Poisson distribution. Although the NB has been found to be able to model over-dispersed data, it cannot handle under-dispersed data. Among those distributions proposed to handle over-dispersed and under-dispersed datasets, the Conway-Maxwell-Poisson (COM-Poisson) and double Poisson (DP) distributions are particularly noteworthy. The DP distribution and its generalized linear model (GLM) framework has seldom been investigated and applied since its first introduction 25 years ago.
The objectives of this study are to: 1) examine the applicability of the DP distribution and its regression model for analyzing crash data characterized by over- and under-dispersion, and 2) compare the performances of the DP distribution and DP GLM with those of the COM-Poisson distribution and COM-Poisson GLM in terms of goodness-of-fit (GOF) and theoretical soundness. All the DP GLMs in this study were developed based on the approximate probability mass function (PMF) of the DP distribution.
Based on the simulated data, it was found that the COM-Poisson distribution performed better than the DP distribution for all nine mean-dispersion scenarios and that the DP distribution worked better for high mean scenarios independent of the type of dispersion. Using two over-dispersed empirical datasets, the results demonstrated that the DP GLM fitted the over-dispersed data almost the same as the NB model and COM-Poisson GLM. With the use of the under-dispersed empirical crash data, it was found that the overall performance of the DP GLM was much better than that of the COM-Poisson GLM in handling the under-dispersed crash data. Furthermore, it was found that the mathematics to manipulate the DP GLM was much easier than for the COM-Poisson GLM and that the DP GLM always gave smaller standard errors for the estimated coefficients.
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Hao, Zhuang. "Casual analysis using two-part models : a general framework for specification, estimation and inference". Diss., 2018. https://doi.org/10.7912/C2F35D.
Testo completoAbstract (sommario):
Indiana University-Purdue University Indianapolis (IUPUI)The two-part model (2PM) is the most widely applied modeling and estimation framework in empirical health economics. By design, the two-part model allows the process governing observation at zero to systematically differ from that which determines non-zero observations. The former is commonly referred to as the extensive margin (EM) and the latter is called the intensive margin (IM). The analytic focus of my dissertation is on the development of a general framework for specifying, estimating and drawing inference regarding causally interpretable (CI) effect parameters in the 2PM context. Our proposed fully parametric 2PM (FP2PM) framework comprises very flexible versions of the EM and IM for both continuous and count-valued outcome models and encompasses all implementations of the 2PM found in the literature. Because our modeling approach is potential outcomes (PO) based, it provides a context for clear definition of targeted counterfactual CI parameters of interest. This PO basis also provides a context for identifying the conditions under which such parameters can be consistently estimated using the observable data (via the appropriately specified data generating process). These conditions also ensure that the estimation results are CI. There is substantial literature on statistical testing for model selection in the 2PM context, yet there has been virtually no attention paid to testing the “one-part” null hypothesis. Within our general modeling and estimation framework, we devise a relatively simple test of that null for both continuous and count-valued outcomes. We illustrate our proposed model, method and testing protocol in the context of estimating price effects on the demand for alcohol.
Libri sul tema "Generalised Maxwell Model"
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Generalized kinetic models in applied sciences: Lecture notes on mathematical problems. Singapore: World Scientific, 2003.
Cerca il testo completoCapitoli di libri sul tema "Generalised Maxwell Model"
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Bobylev, A. V., C. Cercignani e I. M. Gamba. "Generalized Kinetic Maxwell Type Models of Granular Gases". In Mathematical Models of Granular Matter, 23–57. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-78277-3_2.
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Hourahine, Ben, Duncan McArthur e Francesco Papoff. "Principal Modes of Maxwell’s Equations". In The Generalized Multipole Technique for Light Scattering, 1–33. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-74890-0_1.
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Garrett, Steven L. "Elasticity of Solids". In Understanding Acoustics, 179–233. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44787-8_4.
Testo completoAbstract (sommario):
Abstract If a solid is initially at rest and equal and opposing forces are applied to that object, Newton’s Second Law guarantees that the object will remain at rest because the net force on the sample is zero. If that object is an elastic solid, then those forces will cause the solid to deform by an amount that is directly proportional to those applied forces. When the forces are removed, the sample will return to its original shape and size. That reversibility is the characteristic that is required if we say the behavior of the solid is “elastic.” This chapter will quantify the elastic behavior of solids by introducing the concepts of stress and strain and expressing their linear relationship through the definition of elastic moduli that depend only upon the material and the nature of the deformation and not upon the shape of the object. Those concepts allow us to generalize Hooke’s law. As before, the combination of a linear equation of state with Newton’s Second Law will now describe wave motion in solids. The introduction of a relaxation time, through the Maxwell model, will let these results be generalized to viscoelastic materials and then be applied to rubber vibration isolators.
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Wein, O., e L. Zanzotto. "Comparison of the Generalized Maxwell and Stastna Model for Characterizing Dynamic Moduli of Modified Asphalts". In Progress and Trends in Rheology V, 317. Heidelberg: Steinkopff, 1998. http://dx.doi.org/10.1007/978-3-642-51062-5_149.
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Bartoš, O., J. Vlček, M. Plešek e V. Král. "Use of the generalized Maxwell codeformational model for describing plastic melt behaviour during some flow situations". In Progress and Trends in Rheology II, 394–97. Heidelberg: Steinkopff, 1988. http://dx.doi.org/10.1007/978-3-642-49337-9_136.
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"6 Generalized Maxwell models". In Kinetic Equations, 151–94. De Gruyter, 2020. http://dx.doi.org/10.1515/9783110550986-007.
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Anand, Lallit, Ken Kamrin e Sanjay Govindjee. "Three-dimensional linear viscoelasticity under isothermal conditions". In Introduction to Mechanics of Solid Materials, 365–70. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780192866073.003.0022.
Testo completoAbstract (sommario):
Abstract This chapter presents a three-dimensional constitutive equation for isotropic linear viscoelasticity under isothermal conditions in its stress-relaxation integral form. A stress-relaxation function in shear, Gr(t), is introduced, while the bulk response is characterized by a time-independent constant bulk modulus, K. A special Prony series form for Gr(t) based on the generalized Maxwell model is also discussed. The mixed displacement and traction boundary-value problem for isotropic linear viscoelasticity is also discussed. The correspondence principle for three-dimensional problems is also presented.
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Anand, Lallit, Ken Kamrin e Sanjay Govindjee. "Linear viscoelasticity". In Introduction to Mechanics of Solid Materials, 307–39. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780192866073.003.0019.
Testo completoAbstract (sommario):
Abstract This chapter introduces the essential elements of linear viscoelastic material behaviour and modelling in a one-dimensional setting. Stress-relaxation and creep phenomena are discussed and modelled using Boltzmann’s superposition principle, leading to stress-relaxation integral and creep integral forms of the stress-strain relations. A rheological model known as the standard linear solid is introduced, and the resulting kernel functions for stress-relaxation and creep are discussed. The correspondence principle between linear viscoelasticity and linear elasticity is introduced and used to connect relaxation and creep formulations. This principle is also used to discuss the solution of structural problems involving the bending of beams and torsion of shafts made from linear viscoelastic materials. A rheological model known as the generalized Maxwell model together with the attendant Prony series form of the stress-relaxation function are presented, and a time-integration procedure for the resulting constitutive equation for linear viscoelasticity using the Herrmann–Peterson recursion relation is derived.
Atti di convegni sul tema "Generalised Maxwell Model"
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Zhou, Junhao, Daoguo Yang, Fangxian He, Shenhuai Feng e Hengzhi Dong. "Study on the influence of viscoelastic degree of curing of underfill on the warpage of fan-out packaging based on the generalized Maxwell model". In 2024 25th International Conference on Electronic Packaging Technology (ICEPT), 1–5. IEEE, 2024. http://dx.doi.org/10.1109/icept63120.2024.10667662.
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Yang, Qin, Yulu Liu, Haijun Zhang e Chuncheng Zuo. "Derivation of generalized Maxwell velocity slip model". In PROCEEDINGS OF THE 29TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4902618.
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Royston, Thomas J., Soon-Hong Lee e Gary Friedman. "Comparison of Two Rate-Independent Hysteresis Models With Application to Piezoceramic Transducers". In ASME 1999 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/detc99/vib-8082.
Testo completoAbstract (sommario):
Abstract The applicability of and relationship between two rate-independent hysteresis models that have been used to describe hysteresis in piezoceramic transducers are investigated. It is shown that the generalized Maxwell resistive capacitor hysteresis model is a particular case of the classical Preisach hysteresis model. The Preisach function that reduces the Preisach model to the Maxwell resistive capacitor model is derived. It is also shown that the inverse of the Maxwell model is this same particular case of the classical Preisach model. A Maxwell model identification procedure based on Preisach identification principles is formulated. The applicability of the classical Preisach and Maxwell hysteresis models for identifying and simulating piezoceramic dielectric behavior is investigated experimentally via studies on a 1-3 piezoceramic composite. Results indicate that both hysteresis models can accurately represent piezoceramic hysteresis. It is noted that the identified relationship between Preisach and Maxwell hysteresis models may prove useful in a wider range of hysteresis applications than just those involving piezoceramics.
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Renaud, Franck, Gael Chevallier, Jean-Luc Dion e Re´mi Lemaire. "Viscoelasticity Measurement and Identification of Viscoelastic Parametric Models". In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-47545.
Testo completoAbstract (sommario):
Generally speaking, the behaviour of viscoelastic material is more complicated than the behaviour proposed by classical models as Voigt, Maxwell or Zener. The stiffness of such materials is a frequency dependent complex function. Above 1000Hz, classical measurements techniques are unable to achieve accurate measurements of the stiffness. In this paper, a new Dynamical Mechanical Analysis (DMA) tester is presented. It allows the characterization of the shear stiffness of preloaded viscoelastic materials between 200 and 3500Hz and without using frequency-temperature equivalences. Then the Generalized Maxwell model is used to describe behaviours measured with the DMA tester. A new iterative identification method of the parameter of the Generalized Maxwell model is described. This identification method is based on the asymptotes of the model.
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David, N. V., X. L. Gao e J. Q. Zheng. "Creep Behavior of a TWARON®/Natural Rubber Composite". In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-38079.
Testo completoAbstract (sommario):
The creep behavior of a Twaron CT709® fabric/natural rubber composite under a uniaxial constant stress is studied using three viscoelasticity models with different levels of complexity and a newly developed para-rheological model. The three models employed are a one-term generalized Maxwell (GMn = 1) model (consisting of one Maxwell element and an additional spring in parallel), a two-term generalized Maxwell (GMn = 2) model (including two parallel Maxwell elements and an additional spring in parallel), and a four-parameter Burgers model. The values of the parameters involved in each model are extracted from the experimental data obtained in this study. The creep tests reveal that the axial strain starts to increase exponentially during the primary stage and then continues to equilibrate linearly with time. The results show that the initial creep response of the composite is predicted fairly well by the GMn = 2 model, while the secondary creep is more accurately described by the GMn = 1 model. An implicit solution, together with a characteristic retardation time spectrum, obtained using the para-rheological model is found to provide more accurate predictions of the composite creep response than the three viscoelasticity models at both the primary and secondary stages.
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Herrmann, Torsten, e Valdas Chaika. "Identification of Viscoelastic Properties of Finite Element Structures With Joints". In ASME 1997 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/detc97/vib-4246.
Testo completoAbstract (sommario):
Abstract Identification of the damping and stiffness parameters of the composite joints in finite element structures is analyzed. For the modeling of the viscoelastic properties of the joints the classical Voigt-Kelvin and generalized Maxwell model (three parameter solid) are used. A time domain identification algorithm for classically and non-classically damped dynamic systems is developed. It is based on the application of an extended Kalman filter and least square technique. The algorithm uses complex modal analysis and sparse matrix technology. Both force and base excited systems are considered. Experimental verification of the identification results is carried out on a test structure. The accuracy of the modeling of damping in the joint using the Voigt-Kelvin and generalized Maxwell models is investigated.
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David, N. V., X. L. Gao, J. Q. Zheng e K. Masters. "Three-Parameter Viscoelasticity Models for Ballistic Fabrics". In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68853.
Testo completoAbstract (sommario):
Ballistic fabrics are made from high performance polymeric fibers such as Kevlar®, Twaron® and Spectra®. These fibers often behave viscoelastically in high strain rate deformations. The Kelvin-Voigt and Maxwell rheological models have been used to characterize such viscoelastic responses at different strain rates. However, these two-parameter models have been found to be inadequate and inaccurate in some applications. As a result, three-parameter rheological models have been utilized to develop constitutive relations for viscoelastic polymeric fabrics. In this study, a generalized Maxwell (GM) model and a generalized Kelvin-Voigt (GKV) model are proposed to describe the viscoelastic behavior of a ballistic fabric, Twaron® CT716, at the strain rates of 1 s−1 and 495 s−1. The GM model consists of a Maxwell element (including a viscous dashpot and a spring in series) and a second spring in parallel to the Maxwell element, while the GKV model is an assembly of a Kelvin-Voigt (KV) element (containing a viscous dashpot and a spring in parallel) and a second spring in series with the KV element. The predictions by the GM and GKV models are compared with existing experimental data, which shows that the two sets of results are in fairly good agreement. In particular, the comparison reveals that the GKV model gives more accurate results at the low strain rate, whereas the GM model performs better at the high strain rate while still providing accurate predictions for the low strain rate responses.
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Zhang, Wu-Lian. "The generalized Maxwell relaxation model of woven architectural membrane material". In 2016 International Conference on Advanced Materials and Energy Sustainability (AMES2016). WORLD SCIENTIFIC, 2017. http://dx.doi.org/10.1142/9789813220393_0025.
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Costa, M. Fernanda P., e C. Ribeiro. "Generalized fractional Maxwell model: Parameter estimation of a viscoelastic material". In NUMERICAL ANALYSIS AND APPLIED MATHEMATICS ICNAAM 2012: International Conference of Numerical Analysis and Applied Mathematics. AIP, 2012. http://dx.doi.org/10.1063/1.4756256.
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Cao, Danping, e Xingyao Yin. "Q reflections modeling with generalized Maxwell model in time domain". In SEG Technical Program Expanded Abstracts 2011. Society of Exploration Geophysicists, 2011. http://dx.doi.org/10.1190/1.3627780.
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