Relevant bibliographies by topics / Random polymer models

Academic literature on the topic 'Random polymer models'

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Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Random polymer models"

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Jitomirskaya, S., H. Schulz-Baldes, and G. Stolz. "Delocalization in Random Polymer Models." Communications in Mathematical Physics 233, no. 1 (February 1, 2003): 27–48. http://dx.doi.org/10.1007/s00220-002-0757-5.

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Toninelli, Fabio. "Giambattista Giacomin: Random Polymer Models." Journal of Statistical Physics 130, no. 6 (January 8, 2008): 1219–20. http://dx.doi.org/10.1007/s10955-007-9478-7.

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SEMENOFF, GORDON W., and RICHARD J. SZABO. "POLYMER STATISTICS AND FERMIONIC VECTOR MODELS." Modern Physics Letters A 11, no. 14 (May 10, 1996): 1185–97. http://dx.doi.org/10.1142/s0217732396001211.

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We consider a variation of O(N)-symmetric vector models in which the vector components are Grassmann numbers. We show that these theories generate the same sort of random polymer models as the O(N) vector models and that they lie in the same universality class in the large-N limit. We explicitly construct the double-scaling limit of the theory and show that the genus expansion is an alternating Borel summable series that otherwise coincides with the topological expansion of the bosonic models. We also show how the fermionic nature of these models leads to an explicit solution even at finite-N for the generating functions of the number of random polymer configurations.
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Toninelli, Fabio Lucio. "Correlation Lengths for Random Polymer Models and for Some Renewal Sequences." Electronic Journal of Probability 12 (2007): 613–36. http://dx.doi.org/10.1214/ejp.v12-414.

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E. J. Staggs, John. "Discrete population balance models of random agglomeration and cleavage in polymer pyrolysis." AIMS Materials Science 4, no. 3 (2017): 614–37. http://dx.doi.org/10.3934/matersci.2017.3.614.

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Talyigás, Zsófia, and Bálint Vető. "Borodin–Péché Fluctuations of the Free Energy in Directed Random Polymer Models." Journal of Theoretical Probability 33, no. 3 (May 23, 2019): 1426–44. http://dx.doi.org/10.1007/s10959-019-00919-8.

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Tashkinov, M. A., A. D. Dobrydneva, V. P. Matveenko, and V. V. Silberschmidt. "Modeling the Effective Conductive Properties of Polymer Nanocomposites with a Random Arrangement of Graphene Oxide Particles." PNRPU Mechanics Bulletin, no. 2 (December 15, 2021): 167–80. http://dx.doi.org/10.15593/perm.mech/2021.2.15.

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Сomposite materials are widely used in various industrial sectors, for example, in the aviation, marine and automotive industries, civil engineering and others. Methods based on measuring the electrical conductivity of a composite material have been actively developed to detect internal damage in polymer composite materials, such as matrix cracking, delamination, and other types of defects, which make it possible to monitor a composite’s state during its entire service life. Polymers are often used as matrices in composite materials. However, almost always pure polymers are dielectrics. The addition of nanofillers, such as graphene and its derivatives, has been successfully used to create conductive composites based on insulating polymers. The final properties of nanomodified composites can be influenced by many factors, including the type and intrinsic properties of nanoscale objects, their dispersion in the polymer matrix, and interphase interactions. The work deals with modeling of effective electric conductive properties of the representative volume elements of nanoscale composites based on a polymer matrix with graphene oxide particles distributed in it. In particular, methods for evaluating effective, electrically conductive properties have been studied, finite element modelling of representative volumes of polymer matrices with graphene oxide particles have been performed, and the influence of the tunneling effect and the orientation of inclusions on the conductive properties of materials have been investigated. The possibility of using models of resistive strain gauges operating on the principle of the tunneling effect is studied. Based on the finite-element modeling and graph theory tools, we created approaches for estimating changes in the conductive properties of the representative volume elements of a nanomodified matrix subjected to mechanical loading.
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Zhang, Qing Ping, and Zhi Geng Fan. "Numerical Studies on the Dynamic Performance of Polymer Foams." Advanced Materials Research 287-290 (July 2011): 2256–60. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.2256.

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Two-dimensional (2D) regular and random cell models composed of circular cells are developed to simulate the microstructure of polymer foams. Two-parameter Mooney-Rivlin strain energy potential model is employed to characterize the hyperelasticity of the solid of which the foams are made. Finite element method is used to simulate the large deformation of the foams. Numerical results show that the strain rate sensitivity of the polymer foam is weak as rate independent constitutive model is introduced to describe the mechanical performance of cell material. ‘X’-, ‘I’-, and ‘V’-shaped bands are observed in regular foam models at a low, high and moderate impact velocities, respectively; whereas ‘I”-shaped modes appear in random cell models at a high impact velocity only.
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GEURTS, BERNARD J., and FREDERIK W. WIEGEL. "SIMULATION OF THE DYNAMICS OF A MACROMOLECULE IN A RANDOM CONSTRAINT CAGE." Modern Physics Letters B 01, no. 01n02 (May 1987): 57–60. http://dx.doi.org/10.1142/s0217984987000089.

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We determine the centre of mass diffusion coefficient D and the chain relaxation time T of a macromolecule diffusing through a random constraint cage. This cage models the average topological constraints on the motion of a particular polymer, imposed by the other polymers in the system. The constraint cage consists of regularly spaced constraint lines on a cubic lattice which are “active” with a probability p and absent with a probability 1−p. To a good approximation D≈A(p)N−α(p) and T≈B(p)Nβ(p) if N≫1. The exponents α and β show two regions of very rapid change at pc,1≈0.30 and at pc,2≈0.98.
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Hoffmann, Falk, Rainhard Machatschek, and Andreas Lendlein. "Analytical model and Monte Carlo simulations of polymer degradation with improved chain cut statistics." Journal of Materials Research 37, no. 5 (March 3, 2022): 1093–101. http://dx.doi.org/10.1557/s43578-022-00495-4.

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AbstractThe degradation of polymers is described by mathematical models based on bond cleavage statistics including the decreasing probability of chain cuts with decreasing average chain length. We derive equations for the degradation of chains under a random chain cut and a chain end cut mechanism, which are compared to existing models. The results are used to predict the influence of internal molecular parameters. It is shown that both chain cut mechanisms lead to a similar shape of the mass or molecular mass loss curve. A characteristic time is derived, which can be used to extract the maximum length of soluble fragments l of the polymer. We show that the complete description is needed to extract the degradation rate constant k from the molecular mass loss curve and that l can be used to design polymers that lose less mechanical stability before entering the mass loss phase. Graphical abstract
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Dissertations / Theses on the topic "Random polymer models"

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Caravenna, Francesco. "Random walk models and probabilistic techniques for inhomogeneous polymer chains." Paris 7, 2005. http://www.theses.fr/2005PA077092.

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Ortgiese, Marcel. "Stochastic processes in random environment." Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507234.

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We are interested in two probabilistic models of a process interacting with a random environment. Firstly, we consider the model of directed polymers in random environment. In this case, a polymer, represented as the path of a simple random walk on a lattice, interacts with an environment given by a collection of time-dependent random variables associated to the vertices. Under certain conditions, the system undergoes a phase transition from an entropy-dominated regime at high temperatures, to a localised regime at low temperatures. Our main result shows that at high temperatures, even though a central limit theorem holds, we can identify a set of paths constituting a vanishing fraction of all paths that supports the free energy. We compare the situation to a mean-field model defined on a regular tree, where we can also describe the situation at the critical temperature. Secondly, we consider the parabolic Anderson model, which is the Cauchy problem for the heat equation with a random potential. Our setting is continuous in time and discrete in space, and we focus on time-constant, independent and identically distributed potentials with polynomial tails at infinity. We are concerned with the long-term temporal dynamics of this system. Our main result is that the periods, in which the profile of the solutions remains nearly constant, are increasing linearly over time, a phenomenon known as ageing. We describe this phenomenon in the weak sense, by looking at the asymptotic probability of a change in a given time window, and in the strong sense, by identifying the almost sure upper envelope for the process of the time remaining until the next change of profile. We also prove functional scaling limit theorems for profile and growth rate of the solution of the parabolic Anderson model.
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Ou, Zhaoyang. "An association model for specific-interaction effects in random copolymer solutions." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/9140.

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Le, Treut Guillaume. "Models of chromosome architecture and connection with the regulation of genetic expression." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS411/document.

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Plusieurs indices suggèrent que le repliement du chromosome et la régulation de l’expression génétique sont étroitement liés. Par exemple, la co-expression d’un grand nombre de gènes est favorisée par leur rapprochement dans l’espace cellulaire. En outre, le repliement du chromosome permet de faire émerger des structures fonctionnelles. Celles-ci peuvent être des amas condensés et fibrillaires, interdisant l’accès à l’ADN, ou au contraire des configurations plus ouvertes de l’ADN avec quelques amas globulaires, comme c’est le cas avec les usines de transcription. Bien que dissemblables au premier abord, de telles structures sont rendues possibles par l’existence de protéines bivalentes, capable d’apparier des régions parfois très éloignées sur la séquence d’ADN. Le système physique ainsi constitué du chromosome et de protéines bivalentes peut être très complexe. C’est pourquoi les mécanismes régissant le repliement du chromosome sont restés majoritairement incompris.Nous avons étudié des modèles d’architecture du chromosome en utilisant le formalisme de la physique statistique. Notre point de départ est la représentation du chromosome sous la forme d’un polymère rigide, pouvant interagir avec une solution de protéines liantes. Les structures résultant de ces interactions ont été caractérisées à l’équilibre thermodynamique. De plus, nous avons utilisé des simulations de dynamique Brownienne en complément des méthodes théoriques, car elles permettent de prendre en considération une plus grande complexité dans les phénomènes biologiques étudiés.Les principaux aboutissements de cette thèse ont été : (i) de fournir un modèle pour l’existence des usines de transcriptions caractérisées in vivo à l’aide de microscopie par fluorescence ; (ii) de proposer une explication physique pour une conjecture portant sur un mécanisme de régulation de la transcription impliquant la formation de boucles d’ADN en tête d’épingle sous l’effet de la protéine H-NS, qui a été émise suite à l’observation de ces boucles au microscope à force atomique ; (iii) de proposer un modèle du chromosome qui reproduise les contacts mesurés à l’aide des techniques Hi-C. Les conséquences de ces mécanismes sur la régulation de la transcription ont été systématiquement discutées
Increasing evidences suggest that chromosome folding and genetic expression are intimately connected. For example, the co-expression of a large number of genes can benefit from their spatial co-localization in the cellular space. Furthermore, functional structures can result from the particular folding of the chromosome. These can be rather compact bundle-like aggregates that prevent the access to DNA, or in contrast, open coil configurations with several (presumably) globular clusters like transcription factories. Such phenomena have in common to result from the binding of divalent proteins that can bridge regions sometimes far away on the DNA sequence. The physical system consisting of the chromosome interacting with divalent proteins can be very complex. As such, most of the mechanisms responsible for chromosome folding and for the formation of functional structures have remained elusive.Using methods from statistical physics, we investigated models of chromosome architecture. A common denominator of our approach has been to represent the chromosome as a polymer with bending rigidity and consider its interaction with a solution of DNA-binding proteins. Structures entailed by the binding of such proteins were then characterized at the thermodynamical equilibrium. Furthermore, we complemented theoretical results with Brownian dynamics simulations, allowing to reproduce more of the biological complexity.The main contributions of this thesis have been: (i) to provide a model for the existence of transcrip- tion factories characterized in vivo with fluorescence microscopy; (ii) to propose a physical basis for a conjectured regulatory mechanism of the transcription involving the formation of DNA hairpin loops by the H-NS protein as characterized with atomic-force microscopy experiments; (iii) to propose a physical model of the chromosome that reproduces contacts measured in chromosome conformation capture (CCC) experiments. Consequences on the regulation of transcription are discussed in each of these studies
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Krajenbrink, Alexandre. "Beyond the typical fluctuations : a journey to the large deviations in the Kardar-Parisi-Zhang growth model." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEE021.

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Cette thèse de doctorat porte sur l'étude du modèle de croissance stochastique Kardar-Parisi-Zhang (KPZ) en 1+1 dimensions et en particulier de l'équation qui le régit. Cette thèse est d'une part destinée à effectuer un état de l'art et dresser un portrait moderne de la recherche des solutions exactes de l'équation KPZ, de leurs propriétés en terme de théorie des grandes déviations et également de leurs applications (en théorie des matrices aléatoires ou en calcul stochastique notamment). D'autre part cette thèse a pour but de formuler un certain nombre de questions ouvertes à l'interface avec la théorie de l'intégrabilité, la théorie des matrices aléatoires et la théorie des gaz de Coulomb.Cette thèse est divisée en trois parties distinctes portant (i) sur les solutions exactes de l'équation KPZ, (ii) sur les solutions à temps court sous la forme d'un principe grandes déviations et (iii) sur les solutions à temps long et leurs extensions aux statistiques linéaires au bord de spectre de matrice aléatoire.Nous présenterons les résultats de cette thèse comprenant notamment (a) une nouvelle solution de l'équation KPZ à tout temps dans un demi-espace, (b) une méthodologie générale pour établir à temps court un principe de grandes déviations pour les solutions de KPZ à partir de leur représentation sous forme de déterminant de Fredholm et (c) une unification de quatre méthodes permettant d'obtenir à temps long un principe de grandes déviations pour les solutions de l'équation KPZ et de manière plus générale d'étudier des statistiques linéaires au bord du spectre de matrices aléatoires
Throughout this Ph.D thesis, we will study the Kardar-Parisi-Zhang (KPZ) stochastic growth model in 1+1 dimensions and more particularly the equation which governs it. The goal of this thesis is two-fold. Firstly, it aims to review the state of the art and to provide a detailed picture of the search of exact solutions to the KPZ equation, of their properties in terms of large deviations and also of their applications to random matrix theory or stochastic calculus. Secondly, is it intended to express a certain number of open questions at the interface with integrability theory, random matrix theory and Coulomb gas theory.This thesis is divided in three distinct parts related to (i) the exact solutions to the KPZ equation, (ii) the short time solutions expressed by a Large Deviation Principle and the associated rate functions and (iii) the solutions at large time and their extensions to linear statistics at the edge of random matrices.We will present the new results of this thesis including (a) a new solution to the KPZ equation at all times in a half-space, (b) a general methodology to establish at short time a Large Deviation Principle for the solutions to the KPZ equation from their representation in terms of Fredholm determinant and (c) the unification of four methods allowing to obtain at large time a Large Deviation Principle for the solution to the KPZ equation and more generally to investigate linear statistics at the soft edge of random matrices
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Torri, Niccolò. "Phénomènes de localisation et d’universalité pour des polymères aléatoires." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10114/document.

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Le modèle d'accrochage de polymère décrit le comportement d'une chaîne de Markov en interaction avec un état donné. Cette interaction peut attirer ou repousser la chaîne de Markov et elle est modulée par deux paramètres, h et β. Quand β = 0 on parle de modèle homogène, qui est complètement solvable. Le modèle désordonné, i.e. quand β > 0, est mathématiquement le plus intéressant. Dans ce cas, l'interaction dépend d'une source d'aléa extérieur indépendant de la chaîne de Markov, appelée désordre. L'interaction est réalisée en modifiant la loi originelle de la chaîne de Markov par une mesure de Gibbs et la probabilité obtenue définit le modèle d'accrochage de polymère. Le but principal est d'étudier et de comprendre la structure des trajectoires typiques de la chaîne de Markov sous cette nouvelle probabilité. Le premier sujet de recherche concerne le modèle d'accrochage de polymère où le désordre est à queues lourdes et où le temps de retour de la chaîne de Markov suit une distribution sous-exponentielle. Dans notre deuxième résultat nous étudions le modèle d'accrochage de polymère avec un désordre à queues légères et le temps de retour de la chaîne de Markov avec une distribution à queues polynomiales d'exposant α > 0. On peut démontrer qu'il existe un point critique, h(β). Notre but est comprendre le comportement du point critique quand β -> 0. La réponse dépend de la valeur de α. Dans la littérature on a des résultats précis pour α < ½ et α > 1. Nous montrons que α ∈ (1/2, 1) le comportement du modèle dans la limite du désordre faible est universel et le point critique, opportunément changé d'échelle, converge vers la même quantité donnée par un modèle continu
The pinning model describes the behavior of a Markov chain in interaction with a distinguished state. This interaction can attract or repel the Markov chain path with a force tuned by two parameters, h and β. If β = 0 we obtain the homogeneous pinning model, which is completely solvable. The disordered pinning model, i.e. when β > 0, is most challenging and mathematically interesting. In this case the interaction depends on an external source of randomness, independent of the Markov chain, called disorder. The interaction is realized by perturbing the original Markov chain law via a Gibbs measure, which defines the Pinning Model. Our main aim is to understand the structure of a typical Markov chain path under this new probability measure. The first research topic of this thesis is the pinning model in which the disorder is heavy-tailed and the return times of the Markov chain have a sub-exponential distribution. In our second result we consider a pinning model with a light-tailed disorder and the return times of the Markov chain with a polynomial tail distribution, with exponent α > 0. It is possible to show that there exists a critical point, h(β). Our goal is to understand the behavior of the critical point when β -> 0. The answer depends on the value of α and in the literature there are precise results only for the case α < ½ et α > 1. We show that for α ∈ (1/2, 1) the behavior of the pinning model in the weak disorder limit is universal and the critical point, suitably rescaled, converges to the related quantity of a continuum model
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Biswas, Parbati. "Generalized Random Walk Models Of Chain Statistics." Thesis, 1995. http://etd.iisc.ernet.in/handle/2005/1841.

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Johnson, Torrey (Torrey Allen). "Branching random walk and probability problems from physics and biology." Thesis, 2012. http://hdl.handle.net/1957/30268.

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This thesis studies connections between disorder type in tree polymers and the branching random walk and presents an application to swarm site-selection. Chapter two extends results on tree polymers in the infinite volume limit to critical strong disorder. Almost sure (a.s.) convergence in the infinite volume limit is obtained for weak disorder by standard theory on multiplicative cascades or the branching random walk. Chapter three establishes results for a simple branching random walk in connection with a related tree polymer. A central limit theorem (CLT) is shown to hold regardless of polymer disorder type, and a.s. connectivity of the support is established in the asymmetric case. Chapter four contains a model for site-selection in honeybee swarms. Simulations demonstrate a trade-off between speed and accuracy, and strongly suggest that increasing the quorum threshold at which the process terminates usually improves decision performance.
Graduation date: 2013
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Löwe, Henning. "Critical dynamics of gelling polymer solutions." Doctoral thesis, 2004. http://hdl.handle.net/11858/00-1735-0000-0006-B41B-E.

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Books on the topic "Random polymer models"

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R. W. van der Hofstad. One-dimensional random polymers. Amsterdam, The Netherlands: CWI, 1998.

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Giacomin, Giambattista. Random Polymer Models. Imperial College Press, 2007.

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Random Polymer Models. Imperial College Press, 2007.

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Tulino, Antonia, and Sergio Verdu. Random matrix theory and ribonucleic acid (RNA) folding. Edited by Gernot Akemann, Jinho Baik, and Philippe Di Francesco. Oxford University Press, 2018. http://dx.doi.org/10.1093/oxfordhb/9780198744191.013.42.

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This article discusses a series of recent applications of random matrix theory (RMT) to the problem of RNA folding. It first provides a schematic overview of the RNA folding problem, focusing on the concept of RNA pseudoknots, before considering a simplified framework for describing the folding of an RNA molecule; this framework is given by the statistic mechanical model of a polymer chain of L nucleotides in three dimensions with interacting monomers. The article proceeds by presenting a physical interpretation of the RNA matrix model and analysing the large-N expansion of the matrix integral, along with the pseudoknotted homopolymer chain. It extends previous results about the asymptotic distribution of pseudoknots of a phantom homopolymer chain in the limit of large chain length.
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Book chapters on the topic "Random polymer models"

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Comets, Francis. "Log-Gamma Polymer Model." In Directed Polymers in Random Environments, 107–25. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-50487-2_7.

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Ziabicki, Andrzej, and Janusz Walasek. "A Simple Model of Random Tetrafunctional Networks with Defects." In Biological and Synthetic Polymer Networks, 517–30. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-1343-1_36.

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Sperling, L. H. "The “Katz Effect” on the Random Coil Model for Polymer Chains." In Pioneers in Polymer Science, 41–46. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-2407-9_4.

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Koukiou, F. "Directed Polymers in Random Media and Spin Glass Models on Trees." In Classical and Modern Branching Processes, 171–79. New York, NY: Springer New York, 1997. http://dx.doi.org/10.1007/978-1-4612-1862-3_13.

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"Weakly Inhomogeneous Models." In Random Polymer Models, 69–88. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2007. http://dx.doi.org/10.1142/9781860948299_0003.

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"Random Polymer Models and their Applications." In Random Polymer Models, 1–48. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2007. http://dx.doi.org/10.1142/9781860948299_0001.

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"The Homogeneous Pinning Model." In Random Polymer Models, 49–67. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2007. http://dx.doi.org/10.1142/9781860948299_0002.

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"The Free Energy of Disordered Polymer Chains." In Random Polymer Models, 89–99. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2007. http://dx.doi.org/10.1142/9781860948299_0004.

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"Disordered Pinning Models: The Phase Diagram." In Random Polymer Models, 101–25. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2007. http://dx.doi.org/10.1142/9781860948299_0005.

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"Disordered Copolymers and Selective Interfaces: The Phase Diagram." In Random Polymer Models, 127–49. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2007. http://dx.doi.org/10.1142/9781860948299_0006.

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Conference papers on the topic "Random polymer models"

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da Silva, José Luís, and Ludwig Streit. "Form factors for random paths and polymer models a progress report." In STRUCTURE, FUNCTION AND DYNAMICS FROM NM TO GM: Proceedings of the 8th Jagna International Workshop. Author(s), 2017. http://dx.doi.org/10.1063/1.4996513.

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Nargund, Shrikant. "Evaluation of Stress Wave Attenuation in a Polymer Matrix Composite Using Finite Element Analysis Technique." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67055.

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The dynamic behavior of polymer composites is significantly affected by the properties of their micro constituents including shape and size of inclusions and inclusions/matrix adhesion properties. Wave propagation through such a composite is a complex phenomenon as it includes random scattering, absorption and transmittance of the incident wave and is dependent upon factors such as the properties, size and placement of the inclusions inside the matrix. Finite element modeling provides a viable approach for investigating the effects of micro constituent structure on the dynamic behavior of polymer composites. In this paper, we investigate the stress wave attenuation characteristics of a particulate polymer matrix composite using Finite Element (FE) analysis approach. The wave attenuation of ultrasonic sinusoidal waves of frequency ranging from 1 MHz to 4 MHz is evaluated for different FE models. The spherical inclusions are randomly distributed inside the polymer matrix with a certain minimum distance apart from each other. Inclusion-Matrix adhesion properties are studied by modeling a small region at the interface of inclusions and matrix known as interphase region. The interphase region is modeled explicitly using the cohesive zone modeling approach to study how the properties of this region will affect the wave attenuation characteristics of the polymer composite. Cohesive zone models are governed by traction separation law which helps in the measurement of the inclusion-matrix bonding strength and also allow the study of de-bonding at the interface in the critically stressed region produced due application of load. Thus the FE models consist of three phases; polymer matrix, particulate inclusions and the interphase region. Various three dimensional FE models are created using 3D tetrahedral/hexahedral elements by varying the radius of the spherical inclusions and by varying volume fraction of the inclusions. The analyses are performed using a general purpose finite element software LS-Dyna. A rate dependent viscoelastic material model with four terms in prony series expansion is used for modeling the polymer matrix. A linear elastic isotropic material model is used for modeling the inclusions. The wave attenuation is measured as reduction in the amplitude of the wave as it passes through the composite. A comparison of results for various models is done to check for general trend of attenuation coefficient as a function of size of inclusions, volume fraction of inclusions, frequency of loading and interphase region properties. Results show that volume fraction and load frequency have a maximum effect on the wave attenuation coefficient. Interphase region stiffness and interface de-bonding also plays an important role in attenuation characteristics of the polymer composite.
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LEE, JUHYEONG JUHYEONG, and SYED ZULFIQAR HUSSAIN SHAH. "PREDICTING STOCHASTIC LIGHTNING MECHANICAL DAMAGE EFFECTS ON CARBON FIBER REINFORCED POLYMER MATRIX COMPOSITES." In Proceedings for the American Society for Composites-Thirty Seventh Technical Conference. Destech Publications, Inc., 2022. http://dx.doi.org/10.12783/asc37/36374.

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Three stochastic air blast models are developed with spatially varying elastic properties and failure strengths for predicting lightning mechanical damage to AS4/3506 carbon/epoxy composites subjected to < 100 kA peak currents: (1) the conventional weapon effects program (CWP) model, (2) the coupled eulerianlagrangian (CEL) model, and (3) the smoothed-particle hydrodynamics (SPH) model. This work is an extension of our previous studies [1–4] that used deterministic air blast models for lightning mechanical damage prediction. Stochastic variations in composite material properties were generated using the Box-Muller transformation algorithm with the mean (i.e., room temperature experimental data) and their standard deviations (i.e., 10% of the mean herein as reference). The predicted dynamic responses and corresponding damage initiation prediction for composites under equivalent air blast loading were comparable for the deterministic and stochastic models. Overall, the domains with displacement, von-Mises stress, and damage initiation contours predicted in the stochastic models were somewhat sporadic and asymmetric along the fiber’s local orientation and varied intermittently. This suggests the significance of local property variations in lightning mechanical damage prediction. Thus, stochastic air blast models may provide a more accurate lightning mechanical damage approximation than traditional (deterministic) air blast models. All stochastic models proposed in this work demonstrated satisfactory accuracy compared to the baseline models, but required substantial computational time due to the random material model generation/assignment process, which needs to be optimized in future work.
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4

Idogun, Akpevwe Kelvin, Ruth Oyanu Ujah, and Lesley Anne James. "Surrogate-Based Analysis of Chemical Enhanced Oil Recovery – A Comparative Analysis of Machine Learning Model Performance." In SPE Nigeria Annual International Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/208452-ms.

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Abstract Optimizing decision and design variables for Chemical EOR is imperative for sensitivity and uncertainty analysis. However, these processes involve multiple reservoir simulation runs which increase computational cost and time. Surrogate models are capable of overcoming this impediment as they are capable of mimicking the capabilities of full field three-dimensional reservoir simulation models in detail and complexity. Artificial Neural Networks (ANN) and regression-based Design of Experiments (DoE) are common methods for surrogate modelling. In this study, a comparative analysis of data-driven surrogate model performance on Recovery Factor (RF) for Surfactant-Polymer flooding is investigated with seven input variables including Kv/Kh ratio, polymer concentration in polymer drive, surfactant slug size, surfactant concentration in surfactant slug, polymer concentration in surfactant slug, polymer drive size and salinity of polymer drive. Eleven Machine learning models including Multiple Linear Regression (MLR), Ridge and Lasso regression; Support Vector Regression (SVR), ANN as well as Classification and Regression Tree (CART) based algorithms including Decision Trees, Random Forest, eXtreme Gradient Boosting (XGBoost), Gradient Boosting and Extremely Randomized Trees (ERT), are applied on a dataset consisting of 202 datapoints. The results obtained indicate high model performance and accuracy for SVR, ANN and CART based ensemble techniques like Extremely Randomized Trees, Gradient Boost and XGBoost regression, with high R2 values and lowest Mean Squared Error (MSE) values for the training and test dataset. Unlike other studies on Chemical EOR surrogate modelling where sensitivity was analyzed with statistical DoE, we rank the input features using Decision Tree-based algorithms while model interpretability is achieved with Shapely Values. Results from feature ranking indicate that surfactant concentration, and slug size are the most influential parameters on the RF. Other important factors, though with less influence, are the polymer concentration in surfactant slug, polymer concentration in polymer drive and polymer drive size. The salinity of the polymer drive and the Kv/Kh ratio both have a negative effect on the RF, with a corresponding least level of significance.
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5

He, Xingxi, and Donald J. Leo. "Monte-Carlo Simulation of Ion Transport at the Polymer-Metal Interface." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-79765.

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The transport of charge due to electric stimulus is the primary mechanism of actuation for a class of polymeric active materials known as ionomeric polymer transducers. Continuum-based models of ion transport have been developed for the purpose of understanding charge transport due to diffusion and migration. In this work a two dimensional ion hopping model has been built to describe ion transport in ionomeric polymer transducer (IPT) with Monte-Carlo simulation. In the simulation, cations are distributed on 50nm × 50nm × 1nm (or 50nm × 10 nm × 1nm) lattice cells of IPT while the same number of negative charges are uniformly scattered and fixed as background. In the simulation, thermally activated cations are hopping between multiwell energy structures by overcoming energy barriers around with a hopping distance of 1nm during each time step. A step voltage is applied between the electrodes of the IPT. In one single simulation step, coulomb energy, external electric potential energy and intrinsic energy of the material are calculated and added up for the energy wells around the cations. And then hopping rates in every potential hopping direction are obtained. Due to the random nature of the ion transitions, a weighting function from Monte-Carlo algorithm is added in to calculate the ion hopping time. Finally hopping time is compared, the minimum hopping time is chosen and one hopping event is completed. Both system time and ions distribution are updated before the next simulation loop. Periodic boundary conditions are applied when ions hop in the direction perpendicular to the electric field. The influence of the electrodes on both faces of IPT is presented by the method of image charges. The charge density at equilibrium state is compared with the result from a continuum-based model. The property of charge density has charge neutrality over the central part of the membrane and the charge imbalance over boundary layers close to the anode and cathode. Electric field distribution is obtained after charge distribution. After it is demonstrated that ion hopping model leads to the results qualitatively matching the property of IPT, the paper uses the model to analyze the polymer-metal interface when the electrode shape inside transducer varies.
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Yamamoto, Namiko, Hai M. Duong, Aaron J. Schmidt, Brian L. Wardle, Dimitrios V. Papavassiliou, and Shigeo Maruyama. "Simulation of Thermal Conductivity in Fabricated Variable Volume Fraction Aligned Carbon Nanotube Polymer Composites." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-66557.

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Thermal conductivities of aligned carbon nanotube (CNT)–polymer nano-composites were estimated using the off-lattice Monte Carlo simulation. High thermal conductivity to density ratio is theoretically and experimentally recognized as one of the exceptional properties of CNTs. Aligned CNTs combined with existing advanced composites are being explored for macro-scale aerospace structures that benefit from thermal tailoring and light weight. Accurate thermal transport models within different polymer nanocomposites, and larger-scale and complexity composites, remain to be developed. The model previously developed for single-walled nanotube (SWNT)-polymer composites was modified to simulate the thermal property of aligned multi-walled nanotube (MWNT)-polymer nanocomposites of different volume fraction. Random walk simulations of thermal walkers are used to determine the interfacial resistance to heat flow inside the nano-composites in the directions parallel and perpendicular to the CNT alignment axis. The thermal equilibrium factor between the MWNTs and the composite matrix material is also determined numerically in this study. The CNT-polymer samples were fabricated for thermal conductivity measurements using two methods: the pump-and-probe method and the infrared microscopy. Aligned SWNT and MWNT forests were grown using chemical vapor deposition (CVD). The MWNTs were mechanically densified up to ∼20% aligned-CNT volume fraction. The MWNT forests were immersed in an aerospace-grade thermoset resin, and cured. Near future work is to compare the simulated effective thermal conductivities of the CNT-epoxy composites with the measured data of the fabricated specimens to determine thermal boundary resistance between CNTs and the polymer.
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Lloyd, George M., Ying Zhang, Peter Fabo, and Ming L. Wang. "Hybrid Frequency Response Characteristics of a Low-Frequency Charge-Mode PVDF Curvature Sensor Measured With a Random Vibration Method." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/ad-23703.

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Abstract Polyvinylidene fluoride (PVDF) is a semicrystalline polymer exhibiting piezoelectric and pyroelectric properties which has been used for sensing infrared energy and the measurement of high frequency stress and strain, such as shocks. Despite the low material cost, durability, high sensitivity, and fast response, PVDF-based sensors have not been successfully used in sensors for large structures (such as buildings and bridges) with dominant low frequency modes, where these benefits would seem appropriate. One reason is that the low frequency response of the sensor and integrated charge amplifier (the hybrid characteristic of the sensor) has not been adequately measured and modeled. In this paper we report precise measurements of the hybrid frequency response of a charge-mode curvature sensor in the range 0.1–45 (Hz) using a random vibration method in conjunction with a precision displacement stage. The experimentally determined response is compared to a SPICE model. The results show a characteristic high pass response with cutoff in qualitative agreement with the model. However the rolloff appears consistently more rapid, with possible attenuation at high frequencies. These results will be useful for developing more accurate models of the sensor, and to further the use of PVDF in low frequency applications.
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8

Jiang, Zhen, Wei Chen, and Craig Burkhart. "A Hybrid Approach to 3D Porous Microstructure Reconstruction via Gaussian Random Field." In ASME 2012 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/detc2012-71173.

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Obtaining an accurate three-dimensional (3D) structure of a porous microstructure is important for assessing the material properties based on finite element analysis. While directly obtaining 3D images of the microstructure is impractical under many circumstances, two sets of methods have been developed in the literature to generate (reconstruct) 3D microstructure from its 2D images: one characterizes the microstructure based on certain statistical descriptors, typically two-point correlation function and cluster correlation function, and then performs an optimization process to build a 3D structure that matches those statistical descriptors; the other method models the microstructure using stochastic models like a Gaussian random field (GRF) and generates a 3D structure directly from the function. The former obtains a relatively accurate 3D microstructure, but the optimization process can be very computationally intensive, especially for problems with a large image size; the latter generates a 3D microstructure quickly but sacrifices the accuracy. A hybrid optimization approach of modeling the 3D porous microstructure of random isotropic two-phase materials is proposed in this paper, which combines the two sets of methods and hence maintains the accuracy of the correlation-based method with improved efficiency. The proposed technique is verified for 3D reconstructions based on silica polymer composite images with different volume fractions. A comparison of the reconstructed microstructures and the optimization histories for both the original correlation-based method and our hybrid approach demonstrates the improved efficiency of the approach.
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Nazarenko, Lidiia, Aleksandr Chirkov, Henryk Stolarski, and Holm Altenbach. "Application of equivalent cylindrical inhomogeneity to modeling of CNT and analysis of influence of CNT distributions on response of functionally graded structural elements." In The 13th international scientific conference “Modern Building Materials, Structures and Techniques”. Vilnius Gediminas Technical University, 2019. http://dx.doi.org/10.3846/mbmst.2019.081.

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A mathematical model based on the concept of the energy-equivalent inhomogeneity combined with the method of conditional moments (MCM) has been applied to analyze Carbon Nanotube (CNT)-reinforced materials. The idea of the energy-equivalent inhomogeneity is to replace the inhomogeneity and its interphase by a single equivalent inhomogeneity. It is evaluated for cylindrical inhomogeneity with Gurtin-Murdoch surface model and spring layer model of interphases. Inclusion of multiple mechanisms in the description of interphases is applied to the CNT-reinforced materials. The CNT is modeled as a cylindrical high-stiffness surface. A weak zone surrounding the CNT can be modeled by a spring layer. In this case, one Gurtin-Murdoch and one spring layer models would need to be combined. To evaluate the effective properties of CNT-reinforced materials a statistical method, the MCM, has been employed which describes random distribution of CNT’s. Closed-form formulas for the components of the effective stiffness tensor of such composites have been developed. A composite plate weakened by a hole under different types of loading is considered. It is assumed, that the plate made of the polymer with randomly distributed and disoriented CNT’s. Analysis of how various special distributions of CNT concentration affect the response of this plate is performed.
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Gurrum, Siva P., Jie-Hua Zhao, and Darvin R. Edwards. "Design Optimization of Material Properties in a Particle-Filled Composite Material System." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-66646.

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This work presents a methodology implementing random packing of spheres combined with commercial finite element method (FEM) software to optimize the material properties, such as Young’s modulus, Poisson’s ratio, coefficient of thermal expansion (CTE) of two-phase materials used in electronic packaging. The methodology includes an implementation of a numerical algorithm of random packing of spheres and a technique for creating conformal FEM mesh of a large aggregate of particles embedded in a medium. We explored the random packing of spheres with different diameters using particle generation algorithms coded in MATLAB. The FEM meshes were generated using MATLAB and TETGEN. After importing the nodes and elements databases into commercial FEM software ANSYS, the composite materials with spherical fillers and the polymer matrix were modeled using ANSYS. The effective Young’s modulus, Poisson’s ratio, and CTE along different axes were calculated using ANSYS by applying proper loading and boundary conditions. It was found that the composite material was virtually isotropic. The Young’s modulus and Poisson’s ratio calculated by FEM models were compared to a number of analytical solutions in the literature. For low volume fraction of filler content, the FEM results and analytical solutions agree well. However, for high volume fraction of filler content, there is some discrepancy between FEM and analytical models and also among the analytical models themselves.
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Reports on the topic "Random polymer models"

1

Lee, H. K., and S. Simunovic. A Micromechanical Constitutive Model of Progressive Crushing in Random Carbon Fiber Polymer Matrix Composites. Office of Scientific and Technical Information (OSTI), September 1999. http://dx.doi.org/10.2172/754359.

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