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Representation of correlation statistics functions in heterogeneous materials using layered fast spherical harmonics expansion

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COMPUTATIONAL MATERIALS SCIENCE 2010年第1期48卷 133-139页

作者： Li, Dongsheng Khaleel, Moe Sun, Xin Garmestani, Hamid Georgia Inst Technol Sch Mat Sci & Engn Atlanta GA 30332 USA Pacific NW Natl Lab Fundamental & Computat Sci Directorate Richland WA 99352 USA

Statistical correlation function, including two-point function, is one of the popular methods to digitize microstructure quantitatively. This paper investigated how to represent statistical correlations using layered fast spherical harmonics expansion. A set of spherical harmonics coefficients may be used to represent the corresponding microstructures. It is applied to represent carbon nanotube composite microstructures to demonstrate how efficiently and precisely the harmonics coefficients will characterize the microstructure. This microstructure representation methodology will dramatically improve the computational efficiencies for future works in microstructure reconstruction and property prediction. (C) 2009 Elsevier B.V. All rights reserved.

关键词： Statistical continuum mechanics Statistics correlation Spherical harmonics Microstructure representation probability functions

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Grain Size Distributions in Normal Grain Growth

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PRAKTISCHE METALLOGRAPHIE-PRACTICAL METALLOGRAPHY 2010年第11期47卷 618-639页

作者： Zoellner, Dana Streitenberger, Peter Univ Magdeburg Inst Expt Phys Abt Mat Phys D-39106 Magdeburg Germany

An analytical distribution function characterising the grain sizes of polycrystalline microstructures is presented. Contrary to standard mathematical probability functions that are still often used for description of experimentally obtained size distributions, this one is based on a statistical mean-field theory of grain growth and is fully consistent with the fundamental physical conditions of total-volume conservation and the existence of a finite average grain volume. It is found that this distribution function describes the grain size distribution obtained by Monte Carlo Potts model simulations better than standard mathematical distributions. Additionally, two-dimensional plane sections from the simulated three-dimensional grain structures are considered and compared with experimental data, and the analytic size distribution function is also compared with an experimental grain size distribution for pure iron obtained by serial sectioning.

关键词： normal grain growth grain granulation Distribution function FE, PURE Grain structure probability functions Particle size distribution size distribution

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Identification of the Effective Distribution Function for Determination of the Distributed Activation Energy Models Using Bayesian Statistics: Application of Isothermal Thermogravimetric Data

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INTERNATIONAL JOURNAL OF CHEMICAL KINETICS 2010年第11期42卷 641-658页

作者： Jankovic, Bojan Univ Belgrade Fac Phys Chem Belgrade 11001 Serbia

The new procedure for identification of the effective distribution function for determination of the distributed activation energy models, which is based on the Bayesian statistics, has been established. The five different continuous probability functions (exponential, logistic, normal, gamma and Weibull probability functions (the extended set of distributions)) were used for searching the most appropriate reactivity model for two heterogeneous processes: (a) the isothermal reduction process of nickel oxide under hydrogen atmosphere and (b) the isothermal degradation process of bisphenol-A polycarbonate (Lexan) under nitrogen atmosphere. Using the Bayes weights, it was shown that for both processes, the most suitable distributed reactivity model is the Weibull distribution model. The kinetic parameters (ln A, E-a) attached with the Weibull distribution model were calculated for both investigated processes, using three different computational methods (the maximum likelihood method (MLM), the nonlinear regression analysis (NRA), and the posterior mean (the expected value of scale parameter eta, E(eta)). It was shown that there is an excellent agreement between the values of kinetic parameters calculated by the MLM, NRA, and E(eta) approaches. Using Bayes weights, it is possible to discriminate between different probability models and to quantify how well a distribution fits the experimental data. For the formal reactivity model comparison, the use of the (nonnormalized) Jeffreys prior is recommended. (C) 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 641-658, 2010

关键词： probability functions nickel oxides decentralised control hydrogen atmosphere Activation energy Weibull distribution Bayesian Statistics Distribute Bayes Distribution function Kinetic parameters nitrogen protective atmosphere

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Entropy of unequal probability sampling designs

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Statistical Methodology 2010年第2期7卷 84-97页

作者： Grafström, Anton Umeå University Sweden

There exist many designs for unequal probability sampling. In this paper entropy, which is a measure of randomness, is used to compare eight designs. Both old and commonly used designs and more recent designs are included. Several different and general estimates of entropy are presented. In the quest of finding entropy, expressions for the probability function are derived for different designs. One of them is a recent general design called correlated Poisson sampling. Several designs are close to having maximum entropy, which means that the designs are robust. A few designs yield low entropy and should therefore in general be avoided. © 2009 Elsevier B.V. All rights reserved.

关键词： Entropy probability functions Sampling designs Unequal probability sampling

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Robust Fuzzy Observer-based Control for TCP/AQM Network Systems with State Delay

Robust Fuzzy Observer-based Control for TCP/AQM Network Syst...

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American Control Conference

作者： Yuanwei Jing Zhaona Chen Georgi M. Dimirovski Faculty of Information Science and Engineering Northeastern University Shenyang Liaoning 110004 P.R. of China Faculty of Engineering Computer Engg. Dept Dogus University of Istanbul TR-347222 Istanbul Rep. of Turkey

ISBN: (纸本)9781424474264

Active Queue Management (AQM) algorithms have been proposed to address performance degradations of end-to -end congestion control. However, these AQM algorithms present weaknesses for stabilizing delays in heavy loaded networks. In this paper, we describe a novel T-S fuzzy control algorithm to improve best effort TCP/IP Networks performance. In TCP networks, the packet-dropping probability function is considered as a control input. Thus, a TCP/AQM controller is modeled as a time-delay system. The robust observer-based controller is designed to achieve the desired queue size and guarantee the asymptotic stability of the operating point. For the particular TCP network mode, the Lyapunov-Krasovskii function is defined, and the system can be stabilize with the obtained the fuzzy state feedback control law by using linear matrix inequality (LMI). Simulation results show that the derived control strategy is validated.

关键词： Delay systems probability functions observer-based control Workstations asymptotic stability region control strategy Network degradation of performance Fuzzy

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A new approximation for the three-point probability function

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INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES 2009年第21期46卷 3782-3787页

作者： Mikdam, A. Makradi, A. Ahzi, S. Garmestani, H. Li, D. S. Remond, Y. Univ Strasbourg Inst Fluid & Solid Mech IMFS F-67000 Strasbourg France Ctr Rech Publ Henri Tudor L-1855 Luxembourg Luxembourg Georgia Inst Technol Sch Mat Sci & Engn Atlanta GA 30332 USA

Statistical continuum theory based approaches are commonly used for the computation of the effective properties of heterogeneous materials. Statistical distribution and morphology of the microstructure are represented by n-point probability function. One-point probability function statistical representation of the microstructure leads to volume fraction dependent homogenization. However, second and higher order probability functions include the information of phase distribution and morphology. Most statistical based homogenization methods are limited to two-point probability function due to the lack of simple approximation of higher order probability functions that can be easily exploited. In this paper, a new approximation of the three-point probability function is proposed and discussed. The new approximation results are compared to existing approximations from the literature and to the real probability functions calculated from a computer generated two-phase micrographs. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： Statistical continuum Heterogeneous media probability functions

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PROPOSAL OF LIGHTNING RISK ASSESSMENT METHOD BASED ON THE LIGHTNING CURRENT probability FUNCTION FOR RAILWAY POWER SUPPLY SYSTEM

PROPOSAL OF LIGHTNING RISK ASSESSMENT METHOD BASED ON THE LI...

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International Conference on Lightning Protection

作者： Hitoshi Hayashiya Masami Hino Toru Murakami Yoshihisa Nishimura Masahiro Miwa Eiji Yoshino Masayuki Matsumoto East Japan Railway Company

ISBN: (纸本)9781509066797

A novel assessment method of breakdown probability at suspension insulators supposing the railway DC power supply system are proposed in this paper. This method is based on the well known lightning current probability function and comparison of lightning endurance of traction wire system between conventional DC railway and Shinkansen is performed. It proves that the introduction of grounding wire in DC railway power system is able to avoid only 36% of flashover at supporting point. The experimental data to confirm the influence of long tail lightning current on tensioned wire and insulators are also shown.

关键词： Lightning railways ground wire suspension insulator probability functions flashover Electric Power Source insulators lightning current Risk Assessment Experimental data evaluation method currents electric current

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Design and Scheduling of Periodic Multipurpose Batch Plants under Uncertainty

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INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH 2009年第21期48卷 9655-9670页

作者： Pinto-Varela, Tania Barbosa-Povoa, Ana Paula F. D. Novais, Augusto Q. Univ Tecn Lisboa Inst Super Tecn CEG P-1049101 Lisbon Portugal Inst Nacl Engn Tecnol & Inovacao DMS P-1649038 Lisbon Portugal

This work deals with the design of multipurpose batch plants under uncertainty The model proposed by Pinto et al. [Comput. Chem. Eng 2005, 29 (6), 1293-1303] for the detailed design of batch plants is extended to address the problem of uncertainty associated with production demand Equipment choices, as well as plant topology and associated schedule, are defined simultaneously under an uncertain demand environment Uncertainty is treated through a two-stage stochastic model leading to a mixed-integer linear programming (MILP) formulation, where profit is maximized and the expected value of perfect information (EVPI) is determined;the latter is estimated as the difference between the values of profit obtained for the wait-and-see and the here-and-now models A scenario is set up where demand is represented by a discrete probability function and a cyclic operation considered, together with mixed storage policies and sharing of resources. Some illustrative examples are solved to show the model applicability and the EVPI are determined and analyzed.

关键词： probability functions EXPECTATION VALUE loop operation Uncertainty batching machine PINTO Stochastic models

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Effective conductivity in isotropic heterogeneous media using a strong-contrast statistical continuum theory

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2009年第1期57卷 74-86页

作者： Mikdam, A. Makradi, A. Ahzi, S. Garmestani, H. Li, D. S. Remond, Y. Univ Strasbourg Inst Fluid & Solid Mech CNRS IMFS UMR ULP 7507 F-67000 Strasbourg France Georgia Inst Technol Sch Mat Sci & Engn Atlanta GA 30332 USA

The strong-contrast formulation is used to predict the effective conductivity of a porous material. The distribution, shape and orientation of the two phases are taken into account using two- and three-point probability distribution functions. A new approximation for the three-point probability function appropriate for two-phase media is proposed and discussed. Computed results for the effective conductivity using the strong-contrast formulation are compared to the Voigt and the Hashin-Shtrikman upper-bound estimates. These results show that the predicted effective conductivity is lower than both Voigt and Hashin-Shtrikman bounds. Compared to previous results using the weak-contrast formulation, the strong-contrast formulation seems to provide a better estimate for the effect of the microstructure on the conductivity. (C) 2008 Elsevier Ltd. All rights reserved.

关键词： Statistical continuum Heterogeneous media Effective conductivity Strong contrast probability functions

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Method and algorithm for Bayesian estimation of kinetic parameters of chemical processes with fluctuating independent variables

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THEORETICAL FOUNDATIONS OF CHEMICAL ENGINEERING 2009年第6期43卷 861-868页

作者： Meshalkin, V. P. Dovi, V. G. Soboleva, I. V. Mendeleev Univ Chem Technol Russia Moscow Russia Univ Genoa I-16126 Genoa Italy

A method for the calculation of the effect of fluctuations of independent variables on the estimates of kinetic parameters is developed. Fluctuations of variables are random deviations from the accepted constant values or predetermined time dependences. The method is based on the application of the generalized probability function and the Bayesian approach. An algorithm for the realization of the suggested method is also developed. The proposed method and algorithm were used to estimate the kinetic parameters of chemical reactions under temperature fluctuations. The given example is described in detail.

关键词： probability functions computational methods Chemical processes chemical reactions algorithms Bayes methods Independent Variables fluctuations Kinetic parameters

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