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A STATISTICAL-METHOD FOR OPTIMIZING WIND POWER CONTRIBUTION IN A DIESEL SUPPLIED NETWORK

IEE PROCEEDINGS-C GENERATION TRANSMISSION AND DISTRIBUTION 1985年第6期132卷 269-276页

作者： TSITSOVITS, AJ FRERIS, LL UNIV LONDON IMPERIAL COLL SCI & TECHNOL DEPT ELECT ENGNLONDON SW7 2BTENGLAND

Wind energy exploitation is likely to be economically viable in many cases where electricity is generated using diesel fuel. The economics of such cases are examined using statistical methods. The aim is to determine the optimum level of wind power capacity that should be installed in a diesel supplied network on the basis of known facts about the network and about the generation and local wind activity. A model for the load duration curve has to be assumed if not available. The theoretical basis of the method is first described and some details of the computer program to implement the method are given. A generalised study to assess the sensitivity of the solution to a number of parameters provides some interesting insights. Finally, the method is applied to all 45 Greek islands that possess autonomous diesel systems, and it is concluded that, with pessimistic assumptions, fuel savings of up to 22% and net savings of up to 9% are feasible.

关键词： optimisation Other power stations and plants diesel-electric power stations wind power load duration diesel supplied network wind power plants sensitivity electric power generation Power transmission, distribution and supply probability and statistics Diesel power stations and plants transmission networks statistical analysis

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A crystal plasticity model based on transition state theory

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INTERNATIONAL JOURNAL OF PLASTICITY 2017年 93卷 251-268页

作者： Wang, H. Capolungo, L. Clausen, B. Tome, C. N. Los Alamos Natl Lab Mat Sci & Technol Los Alamos NM 87544 USA Georgia Inst Technol George Woodruff Sch Mech Engn Atlanta GA 30332 USA

A crystal plasticity model is developed whereby explicit connections with transition state theory and with the statistics of dislocation arrangements are simultaneously enforced. Leveraging theoretical work on diffraction line profile analysis, the model predicts the distribution of internal stress (or lattice strain) resulting from that of dislocations arrangements. In turn the internal stress distribution is used to predict the activation rate of dislocation unpinning while providing an explicit connection with experimental diffraction line broadening profiles. The newly developed model is implemented into an elastic viscoplastic self-consistent (EVPSC) framework and applied to the case of stainless steel. To clearly demonstrate the additional predictive capabilities of the model, the latter is used to predict the rate sensitivity, stress and strain relaxation, Bauschinger effect, temperature effects, and evolution of the mean and the standard deviation of the lattice strains. It is found that a single set of parameters provides good agreement between the predictions and the corresponding experiments. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Transition state theory Crystal plasticity probability and statistics Polycrystalline material

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Imperfection sensitive strength variation of soil specimens

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 1997年第2期45卷 293-315页

作者： Ikeda, K Chida, T Yanagisawa, E Department of Civil Engineering Tohoku University Sendai 980-77 Japan

The mechanism of the statistical variation of the shearing behavior of soil specimens is investigated from the viewpoint of bifurcation, under the major assumption that these specimens undergo elastic bifurcation, and that such variation is ascribed to the variation of initial imperfections among specimens. Through a synthesis and an extension of the pre-existing bifurcation theory, we advance a method to describe that variation. Two series of triaxial compression tests are conducted to construct a data bank of the shearing behavior of sand specimens. An imperfection sensitivity law is employed to describe the variation in their axial strain versus axial stress curves and volumetric strain versus axial stress curves, and hence to assess the validity of those assumptions to demonstrate the predominant role of elastic bifurcation in soil shearing behavior. The theory of the stochasticity of initial imperfections is employed to explain the probabilistic variation of the maximum strength. (C) 1997 Elsevier Science Ltd.

关键词： buckling granular material asymptotic analysis probability and statistics stability and bifurcation

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PROBABILISTIC TECHNIQUES IN AC LOAD-FLOW ANALYSIS

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PROCEEDINGS OF THE INSTITUTION OF ELECTRICAL ENGINEERS-LONDON 1977年第2期124卷 154-160页

作者： ALLAN, RN ALSHAKARCHI, MRG UNIV MANCHESTER INST SCI & TECHNOLDEPT ELECT ENGN & ELECTRMANCHESTER M60 1QDENGLAND

The paper describes how the previously published formulations for an a.c. probabilistic load-flow analysis can be extended to ensure precise computation of expected values, and how these may be used to obtain more precise values of standard deviations and probability-density curves than was possible thereto. Both of the present formulations linearise the problem around the precise expected value, and one of them accounts for the coupling effect between active and reactive powers. It is shown that this coupling effect may have a significant impact on some of the voltages and reactive powers, but little effect on angles and active powers. A typical system is analysed and discussed to illustrate the increased depth of information that can be gained from these improved techniques.

关键词： load flow analysis probability precise computation of expected values Network and transmission line calculations AC probability and statistics probabilistic techniques power systems load distribution

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Disorder is good for you: the influence of local disorder on strain localization and ductility of strain softening materials

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INTERNATIONAL JOURNAL OF FRACTURE 2017年第2期205卷 139-150页

作者： Tuzes, Daniel Ispanovity, Peter Dusan Zaiser, Michael Eotvos Lorand Univ Dept Mat Phys Pazmany Peter Setany 1-A H-1117 Budapest Hungary Friedrich Alexander Univ Inst Mat Simulat WW8 Dr Mack Str 77 D-90762 Furth Germany

We formulate a generic concept model for the deformation of a locally disordered, macroscopically homogeneous material which undergoes irreversible strain softening during plastic deformation. We investigate the influence of the degree of microstructural heterogeneity and disorder on strain localization (formation of a macroscopic shear band) in such materials. It is shown that increased microstructural heterogeneity delays strain localization and leads to an increase of the plastic regime in the macroscopic stress-strain curves. The evolving strain localization patterns are characterized.

关键词： Fracture Microstructures Inhomogeneous material Numerical algorithms probability and statistics

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Optimizing strength and toughness of nanofiber-reinforced CMCs

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2012年第9期60卷 1688-1702页

作者： Pavia, F. Curtin, W. A. Brown Univ Sch Engn Providence RI 02912 USA Ecole Polytech Fed Lausanne Inst Engn Mech STI IGM GE Stn 9 CH-1006 Lausanne Switzerland

Nanofibers used in current ceramic matrix composites (CMCs) are usually wavy and of finite length. Here, a shear-lag model for predicting the tensile strength and work of fracture of a composite containing a "single matrix crack", as a function of all the material parameters including constant plus Coulomb interfacial friction, is presented for a CMC containing wavy, finite-length nanofibers having a statistical distribution of strengths. Literature results are recovered for straight infinite fibers, with strength and toughness depending on a characteristic strength sigma(c) and a characteristic length delta(c) For nanofibers of finite length L, radius of curvature R, and with Coulomb friction coefficient mu, the strength and toughness are found to depend only on sigma(c), delta(c), and two new dimensionless parameters mu delta(c)/R and L/delta(c). Parametric results for a typical carbon nanotube CMC show an optimal region of morphology (L and R) that maximizes composite strength and toughness, exceeding the properties of composites with straight (R=infinity) and/or long (L=infinity) reinforcements. Therefore, while factors such as the nanofiber strength distribution and the nanofiber-matrix interface sliding resistance may not be easily controlled, the tuning, via processing, of purely geometrical properties of the nanofibers (L and R) alone can aid in maximizing composite properties. These results have important application in hybrid CMCs such as "fuzzy fiber" CMCs, where micron-scale fibers are covered with a forest of nanofibers such that the nanofiber array can bridge longitudinal cracks and thus improve delamination resistance. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Fiber-reinforced composite material Fiber geometry Fracture toughness Analytic functions probability and statistics

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Non-local energetics of random heterogeneous lattices

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2011年第6期59卷 1214-1230页

作者： Zeman, Jan Peerlings, Ron H. J. Geers, Marc G. D. Czech Tech Univ Fac Civil Engn Dept Mech Prague 16629 6 Czech Republic Eindhoven Univ Technol Dept Mech Engn NL-5600 MB Eindhoven Netherlands

In this paper, we study the mechanics of statistically non-uniform two-phase elastic discrete structures. In particular, following the methodology proposed in Luciano and Willis (2005) [Journal of the Mechanics anti Physics of Solids 53, 1505-1522], energetic bounds and estimates of the Hashin-Shtrikman-Willis type are developed for discrete systems with a heterogeneity distribution quantified by second-order spatial statistics. As illustrated by three numerical case studies, the resulting expressions for the ensemble average of the potential energy are fully explicit, computationally feasible and free of adjustable parameters. Moreover, the comparison with reference Monte-Carlo simulations confirms a notable improvement in accuracy with respect to approaches based solely on the first-order statistics. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Inhomogeneous material Structures Energy methods probability and statistics Hashin-Shtrikman-Willis variational principles

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A stochastic study of the collective effect of random distributions of dislocations

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2019年 124卷 10-34页

作者： Gurrutxaga-Lerma, B. Trinity Coll Cambridge Cambridge CB2 1TQ England Univ Cambridge Dept Engn Trumpington St Cambridge CB2 1PZ England

The effect that random populations of dislocations have on a material is examined through stochastic integration of a random cloud of dislocations lying at some distance away from a material point. The problem is studied in one, two, and three dimensions. In 1D, the cloud consists of individual edge dislocations placed along the real line;in 2D, of edge dislocations and edge dipoles on the plane;in 3D, of dislocation loops, In all cases, the dislocation cloud is randomly distributed in space, associated to which several relevant physical parameters, including the material's slip geometry, the dislocation's sign, and its relative orientation, are also stochastically treated. A fully disordered population, i.e., one where the dislocation's signatures and orientations are entirely random, is first studied. It is shown that such disordered systems entail a strong indeterminacy in the collective stress fields, which here is solved by enforcing mass conservation locally. In 2D, this is achieved by modelling a cloud of edge dipoles instead of individual dislocations;in 3D, this is naturally guaranteed by the modelling of closed dislocation loops. The long-range fields of the dipoles in 2D and of the loops in 3D is modelled via their multipolar force expansions, which greatly simplifies the analytical treatment of the problem. The cloud's effect is then studied by performing the stochastic integration of the multipolar fields via Campbell's theorem. The local order, but not the magnitude of the dislocation density, is shown to be critical in contributing to the plastic relaxation of the material: fully disordered systems are shown to self-attenuate, leading to plastic neutrality;ordered and partially ordered systems, achieved when dislocation signatures are aligned, display a direct relationship between the dislocation density and the average stress shielding the material. We establish and generalise the conditions that a system of dislocations must fulfil to display Taylor

关键词： Dislocations Plasticity probability and statistics Point process Scaling laws

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Identification and Asymptotic Localization of Rumor Sources Using the Method of Types

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IEEE TRANSACTIONS ON NETWORK SCIENCE AND ENGINEERING 2020年第3期7卷 1145-1157页

作者： Kesavareddigari, Himaja Spencer, Sam Eryilmaz, Atilla Srikant, R. Ohio State Univ Elect & Comp Engn Dept Columbus OH 43210 USA Univ Illinois Coordinated Sci Lab Urbana IL 61801 USA Univ Illinois Elect & Comp Engn Dept Urbana IL 61801 USA

We are interested in identifying a rumor source on a tree network. We begin with extended star networks under the SI infection model with exponential waiting times. We present and analyze the types center, a highly tractable approximation of the ML source estimate, obtained using the method of types. We empirically show that this approximate ML estimator is exact for some small test cases. We prove that the approximation error is at most logarithmic in infection size on large networks, providing highly efficient source identification (especially compared to the accuracy in similar problems, such as the O(root n) best possible accuracy estimate in a line network). We also show that the qualitative properties of the types and rumor centers are different on extended star networks. We further propose a heuristic-based generalization of this approach to trees: the relative-leaf counting algorithm. In simulations on regular and nonregular trees, types center's performance is competitive with rumor centrality (which is optimal for d-regular trees), while requiring less computation time. In addition to providing a faster (and sometimes more accurate) alternative on its own, our approach could potentially be used with rumor centrality to improve results with less than twice the total computation time.

关键词： Maximum likelihood estimation Heuristic algorithms Computational modeling Partitioning algorithms Mathematical model Approximation algorithms Network problems probability and statistics symbolic and algebraic manipulation performance evaluation of algorithms and systems heuristic design graph and tree search strategies Trees

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REAL-TIME DEMODULATION OF SIGNALS USING STATISTICAL-METHODS

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ELECTRONICS LETTERS 1985年第25-2期21卷 1183-1185页

作者： PRITCHARD, JAS Royal Signals & Radar Establishment Malvern UK

A novel approach to the uncommitted, real-time demodulation of signals using statistical classifiers is described. Preliminary results are presented together with a brief discussion of current work.

关键词： statistical methods Signal processing and detection statistics signal processing probability and statistics Modulation and coding methods real-time demodulation demodulation

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