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Artykuły w czasopismach na temat "Discrete Kinetic System"
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SCHIAVO, M. LO. "DISCRETE KINETIC CELLULAR MODELS OF TUMORS IMMUNE SYSTEM INTERACTIONS". Mathematical Models and Methods in Applied Sciences 06, nr 08 (grudzień 1996): 1187–209. http://dx.doi.org/10.1142/s021820259600050x.
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This paper deals with a kinetic modelling of the cellular dynamics of tumors interacting with an active immune defence system. The analysis starts from the model proposed in Refs. 4 and 5 where a kinetic (cellular) theory of the interactions and competition between tumor cells and immune system is developed in a framework similar to the one of nonlinear statistical mechanics. The class of models proposed in this paper replaces the system of integro-differential equations by a system of ordinary differential equations. This has several advantages. Firstly, it allows immediate interpretations of the control parameters and is characterized by a relatively lower computational complexity. Further, some interesting periodicity properties of the solutions are characterized.
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Papastavridis, J. G. "On the Boltzmann-Hamel Equations of Motion: A Vectorial Treatment". Journal of Applied Mechanics 61, nr 2 (1.06.1994): 453–59. http://dx.doi.org/10.1115/1.2901466.
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This paper presents a direct vectorial derivation of the famous Boltzmann-Hamel equations of motion of discrete mechanical systems, in general nonlinear nonholonomic coordinates and under general nonlinear (velocity) nonholonomic constraints. The connection between particle and system vectors is stressed throughout, in all relevant kinematic and kinetic quantities/principles/theorems. The specialization of these results to the common case of linear nonholonomic coordinates and linear nonholonomic (i.e., Pfaffian) constraints is carried out in the paper’s Appendix.
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STEFANOU, IOANNIS, i JEAN SULEM. "THREE-DIMENSIONAL COSSERAT CONTINUUM MODELING OF FRACTURED ROCK MASSES". Journal of Multiscale Modelling 02, nr 03n04 (wrzesień 2010): 217–34. http://dx.doi.org/10.1142/s1756973710000424.
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The behavior of rock masses is influenced by the existence of discontinuities, which divide the rock in joint blocks making it an inhomogeneous anisotropic material. From the mechanical point of view, the geometrical and mechanical properties of the rock discontinuities define the mechanical properties of the rock structure. In the present paper we consider a rock mass with three joint sets of different dip angle, dip direction, spacing and mechanical properties. The dynamic behavior of the discrete system is then described by a continuum model, which is derived by homogenization. The homogenization technique applied here is called generalized differential expansion homogenization technique and has its roots in Germain's (1973) formulation for micromorphic continua. The main advantage of the method is the avoidance of the averaging of the kinematic quotients and the derivation of a continuum that maps exactly the degrees of freedom of the discrete system through a one-to-one correspondence of the kinematic measures. The derivation of the equivalent continuum is based on the identification for any virtual kinematic field of the power of the internal forces and of the kinetic energy of the continuum with the corresponding quantities of the discrete system. The result is an anisotropic three-dimensional Cosserat continuum.
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Gan, Yanbiao, Aiguo Xu, Guangcai Zhang, Junqi Wang, Xijun Yu i Yang Yang. "Lattice Boltzmann kinetic modeling and simulation of thermal liquid–vapor system". International Journal of Modern Physics C 25, nr 12 (grudzień 2014): 1441002. http://dx.doi.org/10.1142/s0129183114410022.
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We present a highly efficient lattice Boltzmann (LB) kinetic model for thermal liquid–vapor system. Three key components are as below: (i) a discrete velocity model (DVM) by Kataoka et al. [Phys. Rev. E69, 035701(R) (2004)]; (ii) a forcing term Ii aiming to describe the interfacial stress and recover the van der Waals (VDW) equation of state (EOS) by Gonnella et al. [Phys. Rev. E76, 036703 (2007)] and (iii) a Windowed Fast Fourier Transform (WFFT) scheme and its inverse by our group [Phys. Rev. E84, 046715 (2011)] for solving the spatial derivatives, together with a second-order Runge–Kutta (RK) finite difference scheme for solving the temporal derivative in the LB equation. The model is verified and validated by well-known benchmark tests. The results recovered from the present model are well consistent with previous ones [Phys. Rev. E84, 046715 (2011)] or theoretical analysis. The usage of less discrete velocities, high-order RK algorithm and WFFT scheme with 16th-order in precision makes the model more efficient by about 10 times and more accurate than the original one.
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Aregba–Driollet, D., J. Breil, S. Brull, B. Dubroca i E. Estibals. "Modelling and numerical approximation for the nonconservative bitemperature Euler model". ESAIM: Mathematical Modelling and Numerical Analysis 52, nr 4 (lipiec 2018): 1353–83. http://dx.doi.org/10.1051/m2an/2017007.
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This paper is devoted to the study of the nonconservative bitemperature Euler system. We firstly introduce an underlying two species kinetic model coupled with the Poisson equation. The bitemperature Euler system is then established from this kinetic model according to an hydrodynamic limit. A dissipative entropy is proved to exist and a solution is defined to be admissible if it satisfies the related dissipation property. Next, four different numerical methods are presented. Firstly, the kinetic model gives rise to kinetic schemes for the fluid system. The second approach belongs to the family of the discrete BGK schemes introduced by Aregba–Driollet and Natalini. Finally, a quasi-linear relaxation approach and a Lagrange-remap scheme are considered.
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SAIKHANOV, MUSA. "QUANTIZATION OF NONEQUILIBRIUM NONSTATIONARY SYSTEM". International Journal of Modern Physics B 26, nr 12 (8.05.2012): 1241005. http://dx.doi.org/10.1142/s0217979212410056.
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The simultaneous description of nonequilibrium nonstationary system at local and global level is carried out thanks to layering of structure of its energy spectrum. It allows to carry out macroscopic quantization of total production of entropy and to formulate a variation principle. Nonuniformity of energy spectrum nonequilibrium system far from equilibrium state is due to the fact that energy levels in a layer are close to each other (a quasi-continuous spectrum), and the layers are divided by intervals comparable with their width (discrete spectrum). Kinetic processes in system are caused by carrying over of particles and energy between the layers. Quasi-equilibrium subsystems are formed through selective interactions of groups of particles which lead to rapprochement of their values of energies. It allows applying procedure of statistical averaging at local level. As a result, we observe a large-granular quantization at the level of all systems. This approach is applied to kinetic modeling of nonisothermal nonstationary systems.
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Kuznetsov, Alexander A., Anna Yu Tsegelskaya, Pavel V. Buzin, Marina Yu Yablokova i Galina K. Semenova. "High Temperature Polyimide Synthesis in ‘Active’ Medium: Reactivity Leveling of the High and the Low Basic Diamines". High Performance Polymers 19, nr 5-6 (październik 2007): 711–21. http://dx.doi.org/10.1177/0954008307081214.
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The kinetics associated with the reaction of aromatic and aliphatic diamines with phthalic anhydride in glacial acetic acid was studied. This model system was intended to simulate the synthesis of polyimides from diamines and dianhydrides in molten benzoic acid. The reaction proceeds in two discrete steps, the first acylation occurs by the reaction of the diamine with phthalic anhydride followed by cy-clodehydration of the corresponding bis-(o-carboxyamides). The focus of the work was on the influence of chemical composition and basicity of the diamines on the kinetics. Kinetic and thermodynamic characteristics of model reactions were determined. It was established that acylation of aromatic and aliphatic diamines in acid medium proceeds as a reversible second-order reaction catalyzed by acid medium. On the basis of kinetic data obtained, an explanation is given for the observed phenomenon of reactivity leveling of diamines regardless of the basicity.
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DELITALA, MARCELLO, i ANDREA TOSIN. "MATHEMATICAL MODELING OF VEHICULAR TRAFFIC: A DISCRETE KINETIC THEORY APPROACH". Mathematical Models and Methods in Applied Sciences 17, nr 06 (czerwiec 2007): 901–32. http://dx.doi.org/10.1142/s0218202507002157.
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Following some general ideas on the discrete kinetic and stochastic game theory proposed by one of the authors in a previous work, this paper develops a discrete velocity mathematical model for vehicular traffic along a one-way road. The kinetic scale is chosen because, unlike the macroscopic one, it allows to capture the probabilistic essence of the interactions among the vehicles, and offers at the same time, unlike the microscopic one, the opportunity of a profitable analytical investigation of the relevant global features of the system. The discretization of the velocity variable, rather than being a pure mathematical technicality, plays a role in including the intrinsic granular nature of the flow of vehicles in the mathematical theory of traffic. Other important characteristics of the model concern the gain and loss terms of the kinetic equations, namely the construction of a density-dependent table of games to model velocity transitions and the introduction of a visibility length to account for nonlocal interactions among the vehicles.
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Liu, Sheng, Baoling Zhao i Ling Wu. "A Novel MPC with Actuator Dynamic Compensation for the Marine Steam Turbine Rotational Control with a Novel Energy Dynamic Model". Processes 7, nr 7 (3.07.2019): 423. http://dx.doi.org/10.3390/pr7070423.
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The conventional modeling method of the marine steam turbine rotational speed control system (MSTRSCS) is based on Newton’s second law, constructing the mechanical equations between the rotational acceleration and the resultant torque. The disadvantages of this are nonlinearity, a complex structure and an infinite point of discontinuity in the rotational acceleration when the rotational speed is close to 0. Taking the kinetic energy of MSTRSCS as the output variable by using the kinetic energy theorem in this paper, we convert the complex nonlinear model of MSTRSCS into a linear one, since kinetic energy and rotational speed are homeomorphic. Model predictive control (MPC) adopts a discrete-time model, whereas the real system is time-continuous. Hence, poor performance is obtained in the real system when the time-discrete control law is applied to the MSTRSCS through the actuator. In case of high requirements for system accuracy and control performance, conventional MPC (CMPC) cannot meet the engineering requirements. In order to lessen the impact of this phenomenon, this paper proposes a novel MPC with actuator dynamic compensation (ADCMPC), in which the dynamics of the actuator are quantified and the system performance is improved. Compared with other control techniques such as CMPC, the performance of the ADCMPC strategy in MSTRSCS is successfully validated.
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Lima, F. Welington S., i J. A. Plascak. "Kinetic Models of Discrete Opinion Dynamics on Directed Barabási–Albert Networks". Entropy 21, nr 10 (26.09.2019): 942. http://dx.doi.org/10.3390/e21100942.
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Kinetic models of discrete opinion dynamics are studied on directed Barabási–Albert networks by using extensive Monte Carlo simulations. A continuous phase transition has been found in this system. The critical values of the noise parameter are obtained for several values of the connectivity of these directed networks. In addition, the ratio of the critical exponents of the order parameter and the corresponding susceptibility to the correlation length have also been computed. It is noticed that the kinetic model and the majority-vote model on these directed Barabási–Albert networks are in the same universality class.
Rozprawy doktorskie na temat "Discrete Kinetic System"
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Braun, Meire Pereira de Souza. "Modelagem do particulado em sistemas gás-sólido utilizando o modelo de dois fluidos e o método dos elementos discretos". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/18/18149/tde-16092013-160059/.
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A presente pesquisa tem como objetivo realizar um estudo teórico e desenvolver simulações computacionais envolvendo a dinâmica de sistemas gás-sólido. O foco principal do trabalho é a modelagem do particulado através da análise das forças de contato entre partículas de materiais granulares utilizando modelos contínuos baseados na mecânica dos solos e na teoria cinética dos escoamentos granulares (sistemas grandes com muitas partículas, formulação Euleriana - Volumes Finitos) e modelos discretos baseados nas características físicas dos materiais (sistemas intermediários e número limitado de partículas, formulação Lagrangeana - Método dos Elementos Discretos). Investigam-se os modelos existentes na literatura com intuito de melhorar os modelos contínuos e discretos baseados na interação entre as partículas que caracterizam a dinâmica do particulado em sistemas gás-sólido. Propõe-se uma nova abordagem para a determinação do coeficiente de rigidez da mola baseada em uma equivalência entre os modelos lineares e não-lineares. Utiliza-se o código fonte MFIX para realizar simulações computacionais da dinâmica de sistemas gás-sólido, analisando o processo de fluidização, mistura e segregação de partículas, influência das correlações de arrasto, e análise das forças de contato entre as partículas através do novo método para a determinação do coeficiente de rigidez da mola . Os resultados obtidos são comparados com dados numéricos e experimentais da literatura.The purpose of the present study is to perform a theoretical study and develop numerical simulations involving dynamic in gas-solid systems. The focus of the work is the modeling of particulate matter using continuous models based on soil mechanics and the kinetic theory of granular flows (large systems with many particles, Eulerian formulation - Finite Volume) and discrete models based on physical characteristics of the particles (intermediate systems and limited number of particles, Lagrangian formulation - Discrete Element Method). It is proposed a new approach to determine the normal spring stiffness coefficient of the linear model through the numerical solution for the overlap between particles in non-linear models. The linear spring stiffness is determined using an equivalence between the linear and the non-linear models. It is used the MFIX computational code to perform numerical simulations of the dynamics of gas-solid systems. It is analyzed the processes of fluidization, mixing and particle segregation and the influence of drag correlations. The proposed approach for normal spring stiffness coefficient is applied in the numerical simulations of two problems: single freely falling particle and bubbling fluidized bed. The results were compared with numerical and experimental data from literature.
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Raghavendra, Nandagiri Venkata. "Discrete Velocity Boltzmann Schemes for Inviscid Compressible Flows". Thesis, 2017. http://etd.iisc.ac.in/handle/2005/4314.
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It is known that high-speed flows are compressible. In large parts of the flow domains, the inviscid approximation is valid and this leads to Euler equations of gas dynamics. These inviscid compressible flows are modelled by coupled nonlinear hyperbolic systems of partial differential equations and generally require numerical solution techniques, as analytical solutions are usually not available.
Out of all the numerical methods developed over the past five decades to solve the Euler equations, the schemes based on kinetic theory of gases are elegant ones with distinct advantages of simplicity and robustness. However, many kinetic or Boltzmann schemes suffer from high dose of numerical diffusion and these methods are known to be less accurate. The exact shock capturing of steady grid-aligned discontinuities, achieved at the macroscopic level, is yet to be claimed by this class of methods. A closely related class of discrete velocity Boltzmann
schemes proved to be advantageous in this regard, with the first discrete kinetic scheme with exact shock capturing being introduced by Raghurama Rao and Balakrishna[51], by enforcing the Rankine-Hugoniot jump condition at the discrete level. In the first part of this thesis, this accurate shock capturing algorithm with a relaxation system is further improved by various techniques, such as including a diagonal matrix of coefficient of numerical diffusion for vector cases, introducing a wave speed correction mechanism for obtaining physically realistic solutions, introducing a limiter based variant to avoid the use of an entropy _x and finally modifying the numerical diffusion based on the entropy conservation equation to obtain a simple entropy stable and yet accurate discrete velocity Boltzmann scheme. The features of all the new variants are demonstrated by application to several bench-mark test problems.
In the second part of the thesis, a discrete velocity Boltzmann scheme which can capture steady contact discontinuities exactly is developed by using the generalized Riemann invariants together with the jump conditions. This scheme is accurate and widely applicable, without the need for any entropy correction, the relevant features being demonstrated by application to several benchmark test problems.
In the third part of this thesis, a discrete velocity Boltzmann scheme is developed by using physically relevant discrete velocities. A derivation introduced by Sanders and Prendergast [58] is modified to introduce the velocities, of the Dirac delta functions which replace the Maxwellian, matching the eigenvalues at the macroscopic level. This strategy is further coupled with the framework of a discrete velocity Boltzmann system to develop an efficient relaxation scheme for solving the Euler equations. This new algorithm is found to be low in numerical diffusion and also successful in handling various challenging test problems.
Książki na temat "Discrete Kinetic System"
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Discrete Dynamical Systems Chaotic Machines: Theory and Applications. Taylor & Francis Group, 2013.
Znajdź pełny tekst źródłaCzęści książek na temat "Discrete Kinetic System"
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Kolokoltsov, Vassili. "Discrete Kinetic Systems: Equations in l+ p". W Differential Equations on Measures and Functional Spaces, 159–211. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-03377-4_3.
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Piechór, K. "A Discrete Kinetic Model Resembling Retrograde Gases". W Adiabatic Waves in Liquid-Vapor Systems, 227–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-83587-2_20.
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Aregba-Driollet, D., i R. Natalini. "Discrete Kinetic Schemes for Systems of Conservation Laws". W Hyperbolic Problems: Theory, Numerics, Applications, 1–10. Basel: Birkhäuser Basel, 1999. http://dx.doi.org/10.1007/978-3-0348-8720-5_1.
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Fortun, Noel T., Angelyn R. Lao, Luis F. Razon i Eduardo R. Mendoza. "Robustness in Power-Law Kinetic Systems with Reactant-Determined Interactions". W Discrete and Computational Geometry, Graphs, and Games, 106–21. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-90048-9_9.
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Gelnar, Daniel, i Jiri Zegzulka. "Input Parameters – Kinematic Properties". W Discrete Element Method in the Design of Transport Systems, 89–93. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-05713-8_8.
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Light, J. C., R. M. Whitnell, T. J. Park i S. E. Choi. "Quantum Dynamics of Small Systems using Discrete Variable Representations". W Supercomputer Algorithms for Reactivity, Dynamics and Kinetics of Small Molecules, 187–213. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0945-8_11.
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Bulatov, Vasily, i Wei Cai. "Kinetic Monte Carlo Method". W Computer Simulations of Dislocations. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780198526148.003.0014.
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The PN model discussed in the preceding chapter is a continuum approach that requires some atomistic input to account for non-linear interactions in the dislocation core. In this chapter, we introduce yet another continuum model that uses atomistic input for a different purpose. The kinetic Monte Carlo (kMC) model does not consider any details of the core structure but instead focuses on dislocation motion on length and time scales far greater than those of the atomistic simulations. The model is especially effective for diamond-cubic semiconductors and other materials in which dislocation motion is too slow to be observed on the time scale of molecular dynamics simulations. The key idea of the kMC approach is to treat dislocation motion as a stochastic sequence of discrete rare events whose mechanisms and rates are computed within the framework of the transition state theory. Built around its unit mechanisms, the kMC model simulates dislocation motion and predicts dislocation velocity as a function of stress and temperature. This data then can be used to construct accurate mobility functions for dislocation dynamics simulations on still larger scales (Chapter 10). In this sense, kMC serves as a link between atomistic models and coarse-grained continuum models of dislocations. The kMC approach is most useful in situations where the system evolves through a stochastic sequence of events with only a few possible event types. The method has been used in a wide variety of applications other than dislocations. For example, the growth of solid thin films from vapor or in solution is known to proceed through attachment and diffusion of adatoms deposited on the surface. Based on a finite set of unit mechanisms of the motion of adatoms, kMC models accurately describe the kinetics of growth and the resulting morphology evolution of the epitaxial films [95, 96, 97]. Similar kMC models have been applied to dislocation motion in crystals with high lattice resistance, such as silicon. In these materials, dislocations consist of long straight segments interspersed with atomic-sized kinks, depicted schematically in Fig. 9.1(a) as short vertical segments. As was explained in Section 1.3, dislocation motion proceeds through nucleation and migration of kink pairs and can be described well by a kMC model.
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Tuck, Adrian F. "Radiative and Chemical Kinetic Implications". W Atmospheric Turbulence. Oxford University Press, 2008. http://dx.doi.org/10.1093/oso/9780199236534.003.0009.
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The laws governing the dynamical behaviour of atoms and molecules are quantum mechanical, and specify that their internal energy states are discrete, with only definite photon energies inducing transitions between them, subject to selection rules. These energy levels appear as spectra in different regions of the electromagnetic spectrum: pure rotational lines in the microwave or far infrared, ‘rovibrational’ (rotation + vibration) lines in the middle and near infrared, while electronic transitions, sometimes with associated rotational and vibrational structure (‘rovibronic’) occur from the near infrared through the visible to the ultraviolet. An important feature of these spectra in the atmosphere is that they do not appear as single sharp lines, but are collisionally broadened about the central energy into ‘line shapes’ which frequently overlap with other transitions, both from the same molecule and from others. One of the primary dynamical quantities involved in the processes broadening these line shapes is the relative velocity of the molecules with which the photon absorbing and emitting molecules are colliding. These are primarily N2 and O2 in the atmosphere; if they have an overpopulation of fast moving molecules relative to a Maxwell–Boltzmann distribution, as we have suggested, the line shapes will be affected. Molecules such as carbon dioxide, water vapour, and ozone are all active in the infrared via rovibrational transitions, with water vapour being light enough and so having sufficiently rapid rotation that it has rotational bands appearing in the far infrared rather than the microwave. Nitrous oxide, N2O, and methane, CH4, are also active, but make smaller contributions because of their lower abundances. Molecular nitrogen and molecular oxygen, because they are homonuclear diatomic molecules, do not absorb or emit via electric dipole allowed transitions in the atmospherically important regions of the electromagnetic spectrum. Molecular oxygen, having a triplet ground state, does have weak forbidden and magnetic dipole transitions which, however, play only a very small role in the radiative balance. It should be noted that the translational energy of molecules in a large system like the atmosphere is effectively continuous rather than quantized.
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Bischoff, Kenneth B., Abhash Nigam i Michael T. Klein. "Lumping of Discrete Kinetic Systems". W Kinetic and Thermodynamic Lumping of Multicomponent Mixtures, 33–48. Elsevier, 1991. http://dx.doi.org/10.1016/b978-0-444-89032-0.50006-2.
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"Kinetics of Defects in Elastic Dielectrics". W Mechanics and Physics of Discrete Systems, 163–213. Elsevier, 1988. http://dx.doi.org/10.1016/b978-0-444-70299-9.50009-9.
Pełny tekst źródłaStreszczenia konferencji na temat "Discrete Kinetic System"
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Qing, X., W. Xin, Y. Yan i W. Long. "The aggregation rate constant of the discrete population balance model in hot melt fluidized bed coating process". W 21st International Drying Symposium. Valencia: Universitat Politècnica València, 2018. http://dx.doi.org/10.4995/ids2018.2018.7726.
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During hot melt fluidized bed coating, particle agglomeration leads to non-uniform particle size. In this study, Population Balance Model (PBM) is used to establish the conservation of the size of particles in the system. In order to solve the population balance model, it is discretized. The aggregation kernel of the particles can be described by the Equi-partition of Kinetic Energy (EKE) kernel based on the gas dynamics theory. The EKE kernel is incorporated into a discrete population balance (DPB) model, and the effective aggregation rate constant is obtained by fitting with the experimental data. Key words: Hot melt fluidized bed, PBM, DPB, EKE kernel, Aggregation rate constant.
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Liu, Suihan, Nan Hu i Rigoberto Burgueño. "Postbuckling Behavior of Axially-Compressed Strips With Discrete Rigid Constraints: A Numerical Study". W ASME 2015 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/smasis2015-9050.
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Axially-compressed columns, or strips, with bilateral continuous rigid constraints (CRC) are known to be able to attain multiple snap-through buckling events in their elastic postbuckling response that lead to the sudden release of strain energy from the system. This feature allows this structural prototype to be used as energy concentrators for smart applications. However, the parameters controlling the postbuckling response for such system are limited. The structural prototype discussed in this paper is that of an axially compressed strip provided with discrete rigid constraints (DRC), whereby the layout of the lateral constrains provides increased design freedom to control the strip’s postbuckling features. The study is based on numerical simulations using the finite element method. Using a previously characterized CRC strip as a baseline, two DRC design groups were considered in symmetric and asymmetric layouts for a total of 15 different arrangements. Results show that DRC strips can attain elastic postbuckling responses with distinct characteristics and that the far postbuckling response can be controlled by modifying the number and the location of the constraints. Compared to CRC strips, some DRC patterns allow attaining higher mode transitions and larger kinetic energy release after the first buckling event. The ability to design for such postbuckling response features can be potentially used for energy harvesting and other sensing and actuation applications.
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Brown, Forbes T. "Simulating Distributed-Parameter Multiphase Thermodynamic Systems Using Bond Graphs". W ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-39291.
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The use of convection bond graphs with temperature, mass and volume as state variables allows the associated thermodynamic properties of a wide variety of single and multi-phase fluids to be found accurately without iteration, using available formulas. As a result, non-experts can simulate efficiently unsteady systems with compressible flow and heat transfer, as long as the system is modeled with discrete compartments. This paper addresses the discretization of a heat exchanger under changing phase conditions into a finite element model, assuming no slip between phases in thermodynamic equilibrium and neglecting coherent kinetic energy. The staggered grid approach used in conventional numerical analyses for flowing systems is accommodated naturally. Partial upwinding is used to control numerically induced oscillations. The wall shear and the heat transfer are keyed to standard models for laminar and turbulent flow in single-phase and two-phase regimes. A condenser of a refrigeration cycle is given to illustrate the procedure and its results.
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Kim, Joo Youn, Seung Hyup Ryu i Ji Soo Ha. "Numerical Prediction on the Characteristics of Spray-Induced Mixing and Thermal Decomposition of Urea Solution in SCR System". W ASME 2004 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/icef2004-0889.
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The spray-induced mixing characteristics and thermal decomposition of aqueous urea solution into ammonia have been studied to design optimum sizes and geometries of the mixing chamber in SCR (Selective Catalytic Reduction) system. The cold flow tests about the urea-injection nozzle were performed to clarify the parameters of spray mixing characteristics such as mean diameter and velocity of drops and spray width determined from the interactions between incoming air and injected drops. Discrete particle model in Fluent code was adopted to simulate spray-induced mixing process and the experimental results on the spray characteristics were used as input data of numerical calculations. The simulation results on the spray-induced mixing were verified by comparing the spray width extracted from the digital images with the simulated particle tracks of injected drops. The single kinetic model was adopted to predict thermal decomposition of urea solution into ammonia and solved simultaneously along with the verified spray model. The hot air generator was designed to match the flow rate and temperature of the exhaust gas of the real engines. The measured ammonia productions in the hot air generator were compared with the numerical predictions and the comparison results showed good agreements. Finally, we concluded that the design capabilities for sizing optimum mixing chamber were established.
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Thorsley, David. "Diagnosability of stochastic chemical kinetic systems: a discrete event systems approach". W 2010 American Control Conference (ACC 2010). IEEE, 2010. http://dx.doi.org/10.1109/acc.2010.5530522.
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Zhu, Chao, Xiaohua Wang i Guangliang Liu. "Numerical Simulation of Coaxial Evaporating Spray in Nozzle Region of Circulating Fluidized Reactor". W ASME 2002 Joint U.S.-European Fluids Engineering Division Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/fedsm2002-31405.
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Full field hydrodynamic mixing of a coaxial evaporating spray in the nozzle region of a circulating fluidized reactor was numerically investigated. An Eulerian-Lagrangian numerical code was developed for the field description of evaporating spray characteristics with strong phase interactions among evaporating droplets, solids and gas. The gas-solid flow is simulated using multi-fluid method coupled with kinetic theory modeling for inter-particle collisions while the spray is treated as the discrete droplets in a pseudo-continuum gas-solid flow. The Lagrangian simulation of the spray provides the needed coupling terms for the Eulerian simulation of gas-solid flows, such as droplet evaporation rate and interactions among phase of droplets, gas and solids. Phase distributions of temperature, velocity and concentration were achieved to explain the mixing process of evaporating spray in gas-solid flows. Effects of inlet solids loading and droplet size distribution on both spray structure and spray penetration depth were illustrated. An experimental system of liquid nitrogen spray into a circulating fluidized bed of fluid catalytic cracking particles is set up to provide experimental validation of our model. Good comparisons of the simulation and measurements are illustrated.
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Rancruel, Diego, i Michael von Spakovsky. "Development and Application of a Dynamic Decomposition Strategy for the Optimal Synthesis/Design and Operational/Control of a SOFC Based APU Under Transient Conditions". W ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-82986.
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A typical approach to the synthesis/design optimization of energy systems is to only use steady state operation and high efficiency (or low total life cycle cost) at full load as the basis for the synthesis/design. Transient operation is left as a secondary task to be solved by system and control engineers once the synthesis/design is fixed. However, transient regimes may happen quite often and the system response to them is a critical factor in determining the system feasibility. Therefore, it is important to consider the system dynamics in the creative process of developing the system. A dynamic optimization approach developed by the authors and called Dynamic Iterative Local-Global Optimization (DILGO) is applied to the dynamic synthesis/design and operational/control optimization of a solid oxide fuel cell based auxiliary power unit. The approach is based on a decomposed optimization of individual units (components and sub-systems), which simultaneously takes into account the interactions between all the units which make up the overall system. The approach was developed to support and enhance current engineering synthesis/design practices, producing improvements in the initial synthesis/design state of the system and its components at all stages of the process and allowing for any degree of detail (from the simple to the complex) at the unit (component or sub-system) level. The total system is decomposed into three sub-systems: stack sub-system (SS), fuel processing sub-system (FPS), and the work and air recovery sub-system (WRAS). Mixed discrete, continuous, and dynamic operational decision variables are considered. Detailed thermodynamic, kinetic, geometric, physical, and cost models are developed for the dynamic system using advanced state-of-the-art tools. DILGO is then applied to the dynamic synthesis/design and operational/control optimization of the system using total life cycle costs as the objective function. Results for this system and component optimization are presented and discussed.
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Kazemi, Reza, Ali Asghar Jafari i Mohammad Faraji Mahyari. "The Effect of Drilling Mud Flow on the Lateral and Axial Vibrations of Drill String". W ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-25309.
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In this research, the effects of drilling mud flow and WOB force on the lateral vibration of drill string are investigated. To this goal, the kinetic and potential energy of drill string for axial and lateral vibrations are written in an integral equation. In potential energy equation, the effect of geometrical shortening, which causes nonlinear coupling between axial and lateral vibration, is considered. Drilling mud forces are modeled by Paidoussis formulations. The works done by WOB force, weight of drill string and drilling mud forces are calculated. The mode summation method is employed to convert the continuous system to a discrete one. Dropping and considering third and fourth order tensor of potential energy lead to linear and nonlinear system, respectively. The effects of stabilizers are modeled by a linear stiff spring. The wall contact is modeled by Hertzian contact force. Lagrange equation is employed for finding the equations of motions. First and second natural frequencies of drill string are found for different WOB and drilling mud flow. Also the effects of drilling mud and nonlinear terms on lateral vibration of drill string are investigated. The effect of drilling mud on the post buckling vibration of drill string is also delivered. This formulation can be used for optimization of drilling mud flow, WOB and the number and positions of stabilizer so that the lateral vibration of drill string is minimized.
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Parker, Robert G., Shrenik Shah i Lingyuan Kong. "Spatial Discretization of Serpentine Belt Drive Dynamics Using Constrained Basis Functions". W ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32368.
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An efficient method for calculating the eigensolutions and dynamic response of a serpentine belt drive is presented. The model is a hybrid discrete-continuous one where the motions consist of rotations of the pulleys, rotation of the tensioner arm, and transverse vibrations of the continuum belt spans adjacent to the tensioner. The speed of solution results from discretization of the belt spans where the unusual feature is the use of Lagrange multipliers to enforce the geometric boundary conditions at the belt-tensioner interface. The method reduces the computational effort by several orders of magnitude compared to published methods using the same model. Also, it is not susceptible to numerical problems that binder the published methods. The sensitivities of the belt drive natural frequencies to system parameters are also studied. The model parameters under consideration include belt longitudinal stiffness, tensioner spring stiffiness, span tensions, belt transport speed, belt density, and pulley moments of inertia. Exact solutions for the eigensensitivities to these parameters are obtained using perturbation methods. The exact formulae are reduced to simple expressions related to the modal strain and kinetic energies. The eigensensitivities are readily determined, quantitatively and qualitatively, by inspection of the modal energy distributions. An example is presented to demonstrate the capabilities of the methods.
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Cogliati, Joshua J., i Abderrafi M. Ougouag. "Pebble Bed Reactor Dust Production Model". W Fourth International Topical Meeting on High Temperature Reactor Technology. ASMEDC, 2008. http://dx.doi.org/10.1115/htr2008-58289.
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The operation of pebble bed reactors, including fuel circulation, can generate graphite dust, which in turn could be a concern for internal components; and to the near field in the remote event of a break in the coolant circuits. The design of the reactor system must, therefore, take the dust into account and the operation must include contingencies for dust removal and for mitigation of potential releases. Such planning requires a proper assessment of the dust inventory. This paper presents a predictive model of dust generation in an operating pebble bed with recirculating fuel. In this preliminary work the production model is based on the use of the assumption of proportionality between the dust production and the normal force and distance traveled. The model developed in this work uses the slip distances and the inter-pebble forces computed by the authors’ PEBBLES. The code, based on the discrete element method, simulates the relevant static and kinetic friction interactions between the pebbles as well as the recirculation of the pebbles through the reactor vessel. The interaction between pebbles and walls of the reactor vat is treated using the same approach. The amount of dust produced is proportional to the wear coefficient for adhesive wear (taken from literature) and to the slip volume, the product of the contact area and the slip distance. The paper will compare the predicted volume with the measured production rates. The simulation tallies the dust production based on the location of creation. Two peak production zones from intra pebble forces are predicted within the bed. The first zone is located near the pebble inlet chute due to the speed of the dropping pebbles. The second peak zone occurs lower in the reactor with increased pebble contact force due to the weight of supported pebbles. This paper presents the first use of a Discrete Element Method simulation of pebble bed dust production.