Готові списки джерел за темами / 1D diffusion model

Добірка наукової літератури з теми "1D diffusion model"

Автор: Grafiati

Опубліковано: 8 червня 2024

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Статті в журналах з теми "1D diffusion model":

Kim, Hongchul, and Seon-Gyu Kim. "SATURATION ASSUMPTIONS FOR A 1D CONVECTION-DIFFUSION MODEL." Korean Journal of Mathematics 22, no. 4 (December 30, 2014): 599–609. http://dx.doi.org/10.11568/kjm.2014.22.4.599.

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Baro, M., N. Ben Abdallah, P. Degond, and A. El Ayyadi. "A 1D coupled Schrödinger drift-diffusion model including collisions." Journal of Computational Physics 203, no. 1 (February 2005): 129–53. http://dx.doi.org/10.1016/j.jcp.2004.08.009.

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Xu, Yinsheng, Yuhao Xu, Xue Han, Shengping Wang, and Jingxian Yu. "From 1D to 1D–2D–1D: new insights into Li⁺ diffusion behavior in optimized MnO₂ with the cooperative effect of tunnel and interface." Journal of Materials Chemistry A 9, no. 43 (2021): 24397–405. http://dx.doi.org/10.1039/d1ta05108c.

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Larsson, Henrik, and Lars Höglund. "Multiphase diffusion simulations in 1D using the DICTRA homogenization model." Calphad 33, no. 3 (September 2009): 495–501. http://dx.doi.org/10.1016/j.calphad.2009.06.004.

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Elhareef, Mohamed, Zeyun Wu, and Massimiliano Fratoni. "A Consistent One-Dimensional Multigroup Diffusion Model for Molten Salt Reactor Neutronics Calculations." Journal of Nuclear Engineering 4, no. 4 (October 6, 2023): 654–67. http://dx.doi.org/10.3390/jne4040041.

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Molten Salt Reactors (MSRs) have recently gained resurged research and development interest in the advanced reactor community. Several computational tools are being developed to capture the strong neutronics/thermal-hydraulics coupling effect in this special reactor configuration. This paper presents a consistent one-dimensional (1D) multigroup neutron diffusion model for MSR analysis, with the primary aim for fast and accurate calculations for long transients, as well as sensitivity and uncertainty analysis of the reactor. A fictitious radial leakage cross section is introduced in the model to properly account for the radial leakage effects of the reactor. The leakage cross section and other consistent neutronics parameters are generated with the Monte Carlo code Serpent using high-fidelity three-dimensional (3D) models. The accuracy of the 1D consistent model is verified by the reference solution from the Monte Carlo model on the Molten Salt Reactor Experiment (MSRE) configuration. The 1D consistent model successfully reproduced the integrated flux from the 3D model and the reactor multiplication factor keff with the error in the range of 95 to 397 pcm (per cent mille), depending on discretized energy group structures. The developed model is also extended to estimate the reactivity loss due to fuel circulation in MSRE. The estimate of reactivity loss in dynamics analysis is in great agreement with the experimental data. This model functions as the first step in the development of a 1D fully neutronics/thermal-hydraulics coupled model for short- and long-term MSRE transient analysis.

Voges, Jannik, Iryna Smokovych, Fabian Duvigneau, Michael Scheffler, and Daniel Juhre. "Modeling the oxidation of a polymer-derived ceramic with chemo-mechanical coupling and large deformations." Acta Mechanica 233, no. 2 (January 28, 2022): 701–23. http://dx.doi.org/10.1007/s00707-021-03142-x.

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AbstractTo get a better insight into the coating behavior of a polymer-derived ceramic material, we model and simulate the diffusion, oxidation and reaction-induced volume expansion of a specimen without outer mechanical loads. In this macroscale approach, we use an oxidation state variable which determines the composition of the starting material and the oxide material. The model contains a reaction rate which is based on the change of the free energy due to a change of the concentrations of the starting material, the oxide material and a diffusing gaseous material. Using this, we model a growing oxide layer in a perhydropolysilazane (PHPS)-based polymer-derived ceramic (PDC), containing silicon filler particles. Within the mechanical part of the modeling, we use the Neo-Hookean material law which allows for the consideration of volume expansion and the diffusion kinematics in terms of finite deformations. We derive this continuum formulation in 3D and reduce it later to 1D, as we show that a 1D formulation is sufficient for thin oxide layers in our consideration. In such a case, the reaction-induced volume expansion is mostly limited to strains orthogonal to the oxide layer, as the bulk material hinders transversal deformation. Both formulations, i.e., 1D and 3D, are implemented in the finite element software FEAP. We perform a parameter study and fit the results with experimental data. We investigate the diffusion kinematics in the presence of volume expansion. Additionally, we discuss the influence of the elastic energy on the reaction rate.

Navalho, J. E. P., J. M. C. Pereira, and J. C. F. Pereira. "Multi-Scale Modeling of Internal Mass Diffusion Limitations in CO Oxidation Catalysts." Defect and Diffusion Forum 364 (June 2015): 92–103. http://dx.doi.org/10.4028/www.scientific.net/ddf.364.92.

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This work applies a 3D multi-scale bottom-up approach for modeling the processes of diffusion and reaction-diffusion in porous catalyst layers. The performance of the random pore model to predict effective transport coefficients are compared with the results of the multi-scale diffusion model. The results of the 3D multi-scale diffusion model are employed in a 1D pseudo-homogeneous reaction-diffusion model with a relative good agreement with the 3D multi-scale reaction-diffusion model. Furthermore, the former multi-scale model was coupled to a full-scale reactor model with good results and high advantages in terms of computational time savings.

Holmas, H., T. Sira, M. Nordsveen, H. P. Langtangen, and R. Schulkes. "Analysis of a 1D incompressible two-fluid model including artificial diffusion." IMA Journal of Applied Mathematics 73, no. 4 (November 17, 2007): 651–67. http://dx.doi.org/10.1093/imamat/hxm066.

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Herrero-Durá, Iván, Alejandro Cebrecos, Rubén Picó, Vicente Romero-García, Luis Miguel García-Raffi, and Víctor José Sánchez-Morcillo. "Sound Absorption and Diffusion by 2D Arrays of Helmholtz Resonators." Applied Sciences 10, no. 5 (March 2, 2020): 1690. http://dx.doi.org/10.3390/app10051690.

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We report a theoretical and experimental study of an array of Helmholtz resonators optimized to achieve both efficient sound absorption and diffusion. The analysis starts with a simplified 1D model where the plane wave approximation is used to design an array of resonators showing perfect absorption for a targeted range of frequencies. The absorption is optimized by tuning the geometry of the resonators, i.e., by tuning the viscothermal losses of each element. Experiments with the 1D array were performed in an impedance tube. The designed system is extended to 2D by periodically replicating the 1D array. The 2D system has been numerically modeled and experimentally tested in an anechoic chamber. It preserves the absorption properties of the 1D system and introduces efficient diffusion at higher frequencies due to the joint effect of resonances and multiple scattering inside the discrete 2D structure. The combined effect of sound absorption at low frequencies and sound diffusion at higher frequencies, may play a relevant role in the design of noise reduction systems for different applications.

Lugon Junior, Jader, João Flávio Vieira Vasconcellos, Diego Campos Knupp, Gisele Moraes Marinho, Luiz Bevilacqua, and Antônio José da Silva Neto. "Solution of Fourth Order Diffusion Equations and Analysis Using the Second Moment." Defect and Diffusion Forum 399 (February 2020): 10–20. http://dx.doi.org/10.4028/www.scientific.net/ddf.399.10.

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The classical concept of diffusion characterized by Fick’s law is well suited for describing a wide class of practical problems of interest. Nevertheless, it has been observed that it is not enough to properly represent other relevant applications of practical interest. When in a system of particles their spreading is slower or faster than predicted by the classical diffusion model, such a phenomenon is referred to as anomalous diffusion. Time fractional, space fractional and even space-time fractional equations are widely used to model phenomena such as solute transport in porous media, financial modelling and cancer tumor behavior. Considering the effects of partial and temporary retention in dispersion processes a new analytical formulation was derived to simulate anomalous diffusion. The new approach leads to a fourth-order partial differential equation (PDE) and assumes the existence of two concomitant fluxes. This work investigates the behavior of the bi-flux approach in one dimensional (1D) medium evaluating the mean square displacement for different cases in order to classify the diffusion process in normal, sub-diffusive or super-diffusive.

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Дисертації з теми "1D diffusion model":

Sebastian, Ahlberg. "A Monte Carlo study of the particle mobility in crowded nearly one-dimensional systems." Thesis, Umeå universitet, Institutionen för fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-92769.

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The study of crowding effects on particle diffusion is a large subject with implications in many scientific areas. The studies span from pure theoretical calculations to experiments actually measuring the movement of proteins diffusing in a cell. Even though the subject is important and has been studied heavily there are still aspects not fully understood. This report describes a Monte Carlo simulation approach (Gillespie algorithm) to study the effects of crowding on particle diffusion in a quasi one-dimensional system. With quasi meaning that the particles diffuses on a one-dimensional lattice but has the possibility to disassociate from the lattice and then rebind at a latter stage. Different binding strategies are considered: rebinding to the same location and randomly choosing the binding location. The focus of the study is how these strategies affects the mobility (diffusion coefficient) of a tracer particle. The main result of this thesis is a graph showing the diffusion coefficient as a function of the binding rate for different binding strategies and particle densities. We provide analytical estimates for the diffusion coefficient in the unbinding rate limits which show good agreement with the simulations.
Hur "trängsel" (från engelskans "crowding" t ex molecular crowding) påverkar diffusionsprocesser är viktigt inom många olika vetenskapliga områden. Forskningen som för tillfället utförs sträcker sig från rent teoretiska beräkningar till experiments där man kan följa enskilda proteiners rörelse i en cell. Även fast ämnet är viktig och väl undersökt finns det fortfarande många aspekter som man inte förstår till fullo. I det här examensarbetet beskrivs en Monte Carlo metod (Gillespie algoritmen) för att studera hur trängsel påverkar en partikel som diffunderar i ett "nästan" en-dimensonellt system. Det är nästan en-dimensionellt i det avsedde att partiklarna diffunderar på ett gitter men kan binda av från gittret och binda tillbaka i ett senare skedde. Olika metoder för hur partiklarna binder till gittret undersöks: Återbinding till avbindingsplatsen och slumpmässigt vald återbindingsplats. Fokus ligger på att förklara hur dessa påverkar mobiliteten (diffusionskonstanten) av en spårningspartikel (tracer particle). Resultatet är en graf som visar diffusionskonstanten för spårningspartikeln som en funktion av avbindingsfrekvens för olika bindingstrategier och partikeldensiteter. Vi ger också analytiska resultat i gränsvärdet för höga och låga avbindingstakter vilka stämmer bra överens med simuleringar.

Sridhar, Sundaresan. "Study of tokamak plasma disruptions and runaway electrons in a metallic environment." Electronic Thesis or Diss., Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0313.

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Les dispositifs de fusion de type tokamaks ont atteint des performances proches de celles nécessaires à réacteur industriel de fusion et les disruptions sont des événements majeurs dans lesquels l'énergie du plasma est perdue en un très court instant. Electrons découplés (RE), de par leur énergie (quelques 10ème\,MeV), peuvent endommager des composants internes du tokamak. La stratégie actuelle consiste à éviter la génération de RE à l’aide d’une injection massive de matière (MMI). Si leur génération ne peut pas être évitée, une 2ème MMI sera utilisée pour atténuer le faisceau d’électrons découplés. Après la 1ère MMI, un plasma de fond dense et froid d'impuretés MMI est formé et le 2ème MMI visant à atténuer l'emballement du faisceau d'électrons peut être inefficace dans ce plasma de fond, comme observé dans le tokamak JET. Comprendre la physique de l'interaction entre le faisceau d'électrons découplés et le 2ème MMI en présence du plasma de fond froid sera au centre de cette thèse
Tokamaks are the devices currently closest to achieve nuclear fusion power and disruptions are unfavorable events in which the plasma energy is lost in a very short timescale causing damage to tokamak structures. RE beams are one of the consequence of disruptions and they carry the risk of in-vessel component damage. Thus, the prevention and control of the RE are of prime importance. The current strategy for runaway electrons is to avoid their generation by a massive material injection (MMI). If their generation cannot be avoided, a 2nd MMI will be used to mitigate the generated RE beam. After the 1st MMI to prevent RE generation, a background plasma of 1st MMI impurities is formed which make the second MMI inefficient to mitigate RE beams inefficient, as observed in the JET tokamak. In this thesis, the physics of the interaction between the RE beam and the mitigation MMI in the presence of a cold background plasma is studied

Carreira, Ferreira Sonia. "Modélisation du transport intragranulaire dans un réacteur catalytique." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1002/document.

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L'activité chimique des catalyseurs a longuement été le coeur des travaux R&D, conduisant à une influence accrue des limitations diffusionnelles internes. Il est donc important de quantifier et modéliser ces limitations dans le but d'optimiser la conception et les performances des catalyseurs.Dans le cadre de notre projet, en s'appuyant sur une approche de Monte Carlo, des réseaux aléatoires en 2D ou 3D, constitués par des pores cylindriques interconnectés, sont générés de façon à reproduire la porosité, la surface spécifique et le volume poreux des supports d'alumine-gamma. Cet outil est capable de générer des réseaux jusqu'à 18000×18000 noeuds en 2D et 600×600×600 en 3D et contenant 2 milliards de pores. Seulement 4s sont nécessaires à la génération de réseaux 2D carré en 200x200.Un modèle 1D du transport de matière est utilisé à l'échelle du pore en supposant une diffusion fickienne. La diffusion peut être simulée dans des réseaux de taille jusqu'à 200×200. La confrontation des tortuosités simulées aux données de la littérature montre un bon accord. Cependant, la comparaison avec les valeurs expérimentales issues d'études par chromatographie inverse, montre des valeurs expérimentales plus élevées, probablement dû à la présence de deux niveaux de porosité.L'algorithme a par conséquent été modifié afin de générer des réseaux à deux niveaux de porosité et ainsi, reproduire les propriétés texturales et de transfert de matière d'une alumine. Pour un réseau 2D périodique en 100×100, concernant les propriétés texturales, des erreurs relatives inférieures à 10% ont été obtenues. De plus, des tortuosités comparables ont été estimés, 2.34 pour 2.40 expérimentalement
The chemical activity of catalysts has long been the core of R&D studies, leading to an increased influence of internal diffusion limitations. It is therefore important to model and quantify these mass transfer limitations in order to optimize catalyst design and increase performance.In the framework of our project, 2D or 3D pore networks, constituted by interconnected cylindrical pores, are randomly generated by a Monte Carlo approach to reproduce the porosity, specific surface area and pore volume of gamma-alumina supports. A highly efficient tool, capable of generating 2D networks of 18000×18000 and 600×600×600 nodes in 3D, containing up to 2 billion pores. Only 4s are required to generate 2D networks of size 200x200.Mass transfer is simulated by the 1D Fick’s diffusion model within each pore of the network. 200×200 networks, containing up to 80,000 pores, can be simulated. The confrontation of the calculated tortuosities as a function of porosity, to theoretical correlations shows a good agreement. However, when comparing with experimental values from fixed-bed tracer experiments obtained for different gamma-alumina pellets, actual aluminas exhibit higher tortuosities, probably due to the organisation of the porous structure in two levels.Hence, by modifying the developed model to generate two-level networks, we have been able to reproduce both textural and diffusion properties of one alumina. Taking a 2D periodic network of size 100×100 and concerning the textural properties, relative errors less than 10% were obtained. In addition, a good agreement was found for the tortuosity values, 2.34 against the experimental value of 2.40

Частини книг з теми "1D diffusion model":

Allafi, Walid, Ivan Zajic, and Keith J. Burnham. "Identification of Fractional Order Models: Application to 1D Solid Diffusion System Model of Lithium Ion Cell." In Progress in Systems Engineering, 63–68. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-08422-0_9.

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Kamagata, Kiyoto. "A Study of p53 Action on DNA at the Single Molecule Level." In P53 - A Guardian of the Genome and Beyond [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96163.

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The transcription factor p53 searches for and binds to target sequences within long genomic DNA, to regulate downstream gene expression. p53 possesses multiple disordered and DNA-binding domains, which are frequently observed in DNA-binding proteins. Owing to these properties, p53 is used as a model protein for target search studies. It counters cell stress by utilizing a facilitated diffusion mechanism that combines 3D diffusion in solution, 1D sliding along DNA, hopping/jumping along DNA, and intersegmental transfer between two DNAs. Single-molecule fluorescence microscopy has been used to characterize individual motions of p53 in detail. In addition, a biophysical study has revealed that p53 forms liquid-like droplets involving the functional switch. In this chapter, the target search and regulation of p53 are discussed in terms of dynamic properties.

Kamiński, Marcin, and Rafał Leszek Ossowski. "Reaction-Diffusion Problems with Stochastic Parameters Using the Generalized Stochastic Finite Difference Method." In Advances in Computational Intelligence and Robotics, 205–16. IGI Global, 2014. http://dx.doi.org/10.4018/978-1-4666-4991-0.ch010.

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The main aim of this work is to demonstrate the new stochastic discrete computational methodology consisting of the generalized stochastic perturbation technique and of the classical Finite Difference Method for the regular grids to model reaction-diffusion problems with random time series. The generalized stochastic perturbation approach is based on the given order Taylor expansion of all random variables. A numerical algorithm is implemented here using the Direct Differentiation Method of the reaction-diffusion equation with respect to the height of a channel in 1D problem; further symbolic determination of the probabilistic moments and characteristics is completed by the computer algebra system MAPLE, v. 14. Computational illustration attached proves that it is possible to determine using this approach up to the fourth order probabilistic moments and coefficients as well as to consider time series with random coefficients for any dispersion of the input variables. Stochastic fluctuations of the input uncertainty source are defined here as the power time series with Gaussian random coefficients having given first two moments.

Redolfi, M., and M. Tubino. "A diffusive 1D model for the evolution of a braided network subject to varying sediment supply." In River Flow 2014, 1153–61. CRC Press, 2014. http://dx.doi.org/10.1201/b17133-155.

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Тези доповідей конференцій з теми "1D diffusion model":

Schafer, Maximilian, and Rudolf Rabenstein. "A transfer function model for 1D diffusion processes." In 2017 10th International Workshop on Multidimensional (nD) Systems (nDS). IEEE, 2017. http://dx.doi.org/10.1109/nds.2017.8070620.

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Loya, Sudarshan, and Christopher Depcik. "Modifying the Classical 1D Catalyst Model to Include Axial Conduction and Diffusion." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-85740.

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Lean NOx Trap (LNT) catalytic aftertreatment devices are one potential option for the reduction of oxides of nitrogen (NOx) in the exhaust of Compression Ignition engines. They work through a controlled modulation between a storage phase that captures NOx over an alkali earth metal and a regeneration phase that reduces the stored nitrates on the surface using a rich pulse of injected fuel or via stoichiometric engine operation. This rich phase has an associated fuel penalty while being relatively difficult to control through temperature and chemical species. In order to improve system efficiency, a number of researchers have proposed dual leg LNT systems using two LNTs, of which one is always storing while the other is undergoing regeneration. The majority of the exhaust flows through the storage LNT while only a small fraction (low space velocity) advects across the regeneration LNT. This increases the regeneration residence time, improving effectiveness and decreasing the amount of fuel used. From an LNT simulation standpoint, most researchers utilize the classical one-dimensional (1D) aftertreatment model constructed from the Euler equations of motion that neglects axial conduction and diffusion. This paper explores the applicability of this model under low flow situations prevalent in a dual leg LNT system through a carbon monoxide light-off experiment. The authors chose this type of experiment in order to focus purely on fluid mechanics and not the choice of LNT reaction mechanism. The results suggest that a Navier-Stokes (N-S) version of the 1D aftertreatment model is preferred for the regeneration leg of a dual LNT system. Moreover, the authors provide the solution of such a model within this paper.

Skopec, Pavel, Tomas Vyhlidal, and Jan Knobloch. "Reduced model of boundary value dynamics of 1D diffusion - application to heat conduction." In 2021 23rd International Conference on Process Control (PC). IEEE, 2021. http://dx.doi.org/10.1109/pc52310.2021.9447522.

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Zhang, J. "A coupled thermo-mechanical and neutron diffusion numerical model for irradiated concrete." In AIMETA 2022. Materials Research Forum LLC, 2023. http://dx.doi.org/10.21741/9781644902431-4.

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Abstract: Neutron irradiation plays an important role in nuclear-induced degradation for concrete shielding materials, specifically in determining the radiation induced volume expansion (RIVE) phenomenon driving its failure. When analyzing at the structural level the effects of nuclear radiation on concrete, a non-uniformed distribution of neutron radiation must be considered. This can be done via particle transport calculations preventive to the thermo-mechanic study, or by solving numerically the coupled set of governing equations of the problem. In this work the second approach is pursued in the theoretical framework of the Finite Element Method (FEM). The proposed formulation not only considers an accurate neutron transport model based on the two-group theory, but also it includes the effects induced by thermal neutrons to the temperature field. The formulation lends itself to include RIVE and the other relevant radiation induced effects on the mechanical field. The governing equations are presented and discussed, and some results obtained by using the general 3D numerical formulation proposed herein are compared to results from literature obtained via analytical methods addressing simplified 1D problems.

Muratori, Matteo, Ning Ma, Marcello Canova, and Yann Guezennec. "A 1+1D Thermal Dynamic Model of a Li-Ion Battery Cell." In ASME 2010 Dynamic Systems and Control Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/dscc2010-4199.

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Li-ion batteries are today considered the prime solution as energy storage system for EV/PHEV/HEV, due to their high specific energy and power. Since their performance, life and reliability are influenced by the operating temperature, great interest has been devoted to study different cooling solutions and control algorithms for thermal management. In this context, this paper presents a computationally efficient modeling approach to characterize the internal temperature distribution of a Li-ion battery cell, conceived to serve as a tool to aid the design of cooling systems and the development of thermal management systems for automotive battery packs. The model is developed starting from the unsteady heat diffusion equation, for which an analytical solution is obtained through the integral transform method. First, a general one-dimensional thermal model is developed to predict the temperature distribution inside a prismatic Li-ion battery cell under different boundary conditions. Then, a specific case with convective boundary conditions is studied with the objective of characterizing a cell cooled by a forced air flow. To characterize the effects of the cooling system on the temperature distribution within the cell, the one-dimensional solution is then extended to a 1+1D model that accounts for the variability of the boundary conditions in the flow direction. The calibration and validation of the specific model presented will be presented, adopting a detailed 2D FEM simulator as a benchmark.

Asle-Zaeem, Mohsen, and Sinisa Dj Mesarovic. "Finite Element Modeling of a Diffusion-Controlled Phase Transformation in Thin Film." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-66767.

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We derive and implement a finite element (FE) model for stress-mediated diffusion and phase transformation in thin films. The partial differential equations governing diffusion and mechanical equilibrium are of different order. To ensure uniform convergence of the FE method, the continuity class of respective interpolation functions must be different. We test our implementation on a 1D problem and demonstrate the validity of the approach.

He, Jinglin, and Song-Yul Choe. "Modeling a Two-Phase Control-Oriented Transient Model of a Single PEM Fuel Cell." In ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2010. http://dx.doi.org/10.1115/fuelcell2010-33310.

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This paper proposed a 1D non-isothermal control-oriented transient model of PEM fuel cell unit considering the two-phase water dynamics in gas flow channel, gas diffusion layer, catalyst layer and membrane. It is known that the accumulated liquid water in the gas flow channels can block the transport path in the gas diffusion layer for the reactant gases and degrade the performance of the fuel cell, while the proper water amount in the gas flow channels and other layers can help to maintain high proton conductivity in the membrane. The I-V curve and the change of gas concentrations, liquid water amount and temperature at specific operating conditions are obtained by sweeping the current of fuel cell. The voltage, gas concentration, temperature and water dynamic changes are investigated by applying the step change of the load current. The fuel cell performance affected by temperature and water dynamics is studied by the analysis of the simulation result.

Liu, Dehao, Gang Wang, Zhenguo Nie, and Yiming (Kevin) Rong. "Numerical Simulation of the Austenitizing Process in Hypoeutectoid Fe-C Steels." In ASME 2014 International Manufacturing Science and Engineering Conference collocated with the JSME 2014 International Conference on Materials and Processing and the 42nd North American Manufacturing Research Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/msec2014-3948.

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For predicting of diffusive phase transformations during the austenitizing process in hypoeutectoid Fe-C steels, a two-dimensional model has been developed. The diffusion equations are solved within each phase (α and γ) using an explicit finite volume technique formulated using a square grid. The discrete α/γ interface is represented by special volume elements α/γ. The result showing the dissolution of ferrite particles in the austenite matrix are presented at different stages of the phase transformation. Specifically, the influence of the microstructure scale and heating rate on the transformation kinetics has been investigated. Final austenitization temperature calculated with this 2D model is compared with predictions of a simpler one dimensional (1D) front-tracking calculation.

Schor, Alisha R., and H. Harry Asada. "Approximating a MIMO, 1D Diffusion System to a Low Order, State-Space Form in Order to Facilitate Controller Design." In ASME 2010 Dynamic Systems and Control Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/dscc2010-4071.

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Chemical distribution is an important factor in many biological systems, driving the phenomenon known as chemotaxis. In order to properly study the effects of various chemical inputs to an in vitro biological assay, it is necessary to have strict control over the spatial distribution of these chemicals. This distribution is typically governed by diffusion, which by nature is a distributed parameter system (DPS), dependent on both space and time. Much study and literature within the controls community has been devoted to DPS, whose dynamics are marked by partial differential equations or delays. They span an infinite-dimensional state-space, and the mathematical complexity associated with this leads to the development of controllers that are often highly abstract in nature. In this paper, we present a method of approximating these systems and expressing them in a manner that makes a DPS amenable to control using a very low order model. In particular, we express the PDE for one-dimensional chemical diffusion as a two-input, two-output state-space system and show that standard controllers can manipulate the outputs of interest, using pole placement and integral control via an augmented state model.

Liu, Qingyun, Qiangu Yan, and Junxiao Wu. "PEM Fuel Cell Models Validation and Accuracy Analysis." In ASME 2005 3rd International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2005. http://dx.doi.org/10.1115/fuelcell2005-74088.

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A multi-resolution method is developed for the polymer electrolyte membrane (PEM) fuel cell simulation. A full 3D modeling is employed for membrane and diffusion layer, 1D+2D model is applied to the catalyst layer, that is, at each location of the fuel cell plate, the governing equations are integrated only in the direction perpendicular to the fuel cell plate; and a quasi-1D method with high numerical efficiency and reasonable accuracy is employed for the flow channels. The simulation accuracy was assessed in terms of fuel cell polarization curves and membrane ohmic overpotential. Overall, the agreements between simulated results and experimental data are good. However, at large current densities, when high relative humidity reactant inputs are employed, the simulation under predicts the fuel cell performance due to a single-phase assumption. The method slightly over predicts the fuel cell performance for a dry cathode input, possibly due to the nonlinearity of the membrane properties in dehydration case. Further, a parameter study was performed for a fully humidified cell and a relative dry cell. These parameters include porosity and permeability of gas diffusion layer; porosity, effective oxygen permeability, ratio of thickness of surrounding Nafion layer to exposed agglomerate area density and cathodic transfer coefficient of catalyst layer. Some insight can be obtained by examining their effects on the cell performances in order to further improve the model accuracy.