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MOMENT-MEASURING FILTER WITH APPLICATION TO PATTERN RECOGNITION

PROCEEDINGS OF THE INSTITUTION OF ELECTRICAL ENGINEERS-LONDON 1966年第5期113卷 903-&页

作者： HILLER, J University of New South Wales Sydney Australia

The paper discusses the measurement of simple and central moments of a one-dimensional density function. It is found that, if the incident function is multiplied by a scaling function which varies exponentially with time, these moments may be evaluated by the use of a circuit having repeated eigenvalues. A measuring system to evaluate the simple moments is synthetised, and it is indicated how this may be modified to find the central moments. The system obtained may be readily realised on an analogue computer. The relevance of these measurements to the problem of pattern recognition is discussed.

关键词： identification and modelling mathematics probability and statistics analogue computers measurement Control applications Simulation, modelling and identification statistics filters automatic control Self-adjusting control systems self-adjusting systems

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Modification of Mohr's criterion in order to consider the effect of the intermediate principal stress

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INTERNATIONAL JOURNAL OF PLASTICITY 2018年 108卷 40-54页

作者： Comanici, Ana Maria Barsanescu, Paul Doru Gheorghe Asachi Tech Univ Iasi Romania Dept Mech Engn Mechatron & Robot Blvd Mangeron 63 Iasi 700050 Romania

Mohr-Coulomb (M-C) criterion is widely used for isotropic brittle materials, although it has some disadvantages which limit its wider application. One important disadvantage of this theory is that it ignores the effect of the intermediate principal stress, although it has an important influence on materials behaviour. Therefore, Mohr-Coulomb theory is actually used only for materials in biaxial state of stress. In this paper, a modified form of Mohr's criterion has been suggested, in order to overcome this limitation. The modified criterion takes into account the influence of intermediate principal stress in the case of materials under triaxial loading conditions. On the basis of two new hypotheses, a real triaxial state of stress is replaced by a virtual biaxial state of stress. The above mentioned stress states are considered to be equivalent for a material when the failure is imminent in both cases. Both Mohr's theory and the concept of equivalence of stress states are combined in order to obtain the virtual biaxial state of stress, which is determined using all three principal stresses. The modified Mohr's theory can be used only for triaxial state of stress. For biaxial and uniaxial state of stress it is reduced to the classical one. The proposed hypotheses have an important advantage because does not require additional material coefficients. The calculated values using the virtual biaxial state of stress and the linear M-C criterion are in good agreement with experimental data for grey cast iron. The article also presents a compact statistical analysis for both stresses and errors, in order to objectively assess the effectiveness of the formulated hypotheses.

关键词： Yield condition Metallic material Analytic functions probability and statistics Virtual Mohr circle Intermediate principal stress

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Neural Sequence Transformation

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COMPUTER GRAPHICS FORUM 2021年第7期40卷 131-140页

作者： Mukherjee, Sabyasachi Mukherjee, Sayan Hua, Binh-Son Umetani, Nobuyuki Meister, Daniel Univ Tokyo Tokyo Japan Univ Illinois Chicago IL 60680 USA Blueqat Co Ltd Tokyo Japan VinAI Res Hanoi Vietnam VinUniversity Hanoi Vietnam

Monte Carlo integration is a technique for numerically estimating a definite integral by stochastically sampling its integrand. These samples can be averaged to make an improved estimate, and the progressive estimates form a sequence that converges to the integral value on the limit. Unfortunately, the sequence of Monte Carlo estimates converges at a rate of O(root n), where n denotes the sample count, effectively slowing down as more samples are drawn. To overcome this, we can apply sequence transformation, which transforms one converging sequence into another with the goal of accelerating the rate of convergence. However, analytically finding such a transformation for Monte Carlo estimates can be challenging, due to both the stochastic nature of the sequence, and the complexity of the integrand. In this paper, we propose to leverage neural networks to learn sequence transformations that improve the convergence of the progressive estimates of Monte Carlo integration. We demonstrate the effectiveness of our method on several canonical 1D integration problems as well as applications in light transport simulation.

关键词： CCS Concepts • Mathematics of computing → Numerical analysis probability and statistics • Computing methodologies → Machine learning algorithms Ray tracing

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Probabilistic fracture of Ti-6Al-4V made through additive layer manufacturing

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INTERNATIONAL JOURNAL OF PLASTICITY 2016年 78卷 145-172页

作者： Tancogne-Dejean, Thomas Roth, Christian C. Woy, Udisien Mohr, Dirk Ecole Polytech Dept Mech Solid Mech Lab CNRSUMR 7649 Palaiseau France MIT Dept Mech Engn Impact & Crashworthiness Lab Cambridge MA 02139 USA Swiss Fed Inst Technol Dept Mech & Proc Engn Zurich Switzerland Univ Sheffield Adv Mfg Res Ctr Sheffield S10 2TN S Yorkshire England

The large deformation response of Ti-6Al-4V parts made through additive layer manufacturing is investigated. A wire-feed process is chosen instead of a powder process in an attempt to reduce the oxide contaminations of the final part. The experimental program includes uniaxial tension experiments along different part directions and fracture experiments on flat specimens with cut-outs covering stress states ranging from pure shear to equi-biaxial tension. More than 100 experiments are performed in total to characterize the randomness in the material's fracture response. It is found that the stress strain response of the ALM material is comparable to that of Ti-6Al-4V sheet stock, while its average ductility is substantially lower. For example, for pure shear loading, the average strain to fracture for the ALM material is 0.47, while the mill product of the same alloy failed at a strain of 0.65. A probabilistic extension of the stress state dependent Hosford Coulomb fracture initiation model is proposed to account for the significant standard deviation in the identified strains to fracture. Microscopic and surface strain field analysis demonstrate that the initiation and propagation of ductile fracture in the ALM material is strongly affected by the presence of prior-beta grains. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Fracture Anisotropic material probability and statistics Hosford-Coulomb

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Identification of material parameters for inelastic constitutive models: statistical analysis and design of experiments

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INTERNATIONAL JOURNAL OF PLASTICITY 2004年第8-9期20卷 1403-1440页

作者： Harth, T Schwan, S Lehn, J Kollmann, FG Tech Univ Darmstadt Dept Math D-64289 Darmstadt Germany

In this paper we introduce stochastic methods to describe the influence of scattering test data on the identification of material parameters. We employ the viscoplastic constitutive model of Chan, Bodner, and Lindholm in its uniaxial form. The available test data result from three types of experiments performed at 600 degreesC on AINSI SS316 stainless steel, namely creep tests, constant strain rate tension tests with intermediate relaxation, and cyclic tension-compression tests. Each test has been performed with 12 specimens at different strain rates and stress rates respectively. However, for a serious statistical evaluation a larger number of experiments is required. In order to increase the number of tests we introduce stochastic simulations based on time series analysis which generate artificial data with the same stochastic behaviour as the experimental data. The method of stochastic simulation presents a widely accepted technique in engineering which does not add complexity to the process of parameter identification, but allows an investigation of the confidence in the fits of the material parameters. To keep the computation time for the identification of the material parameters as low as possible, very efficient numerical methods have to be implemented. The methods applied here for integration and nonlinear optimization are briefly introduced. The optimization strategy contains stochastic elements. Furthermore, we apply the method of statistical design of experiments to derive which combination of tests yields the most important information for an effective identification of material parameters. (C) 2003 Elsevier Ltd. All rights reserved.

关键词： viscoplastic material constitutive behaviour optimization, parameter identification probability and statistics

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Probabilistic multiscale models and measurements of self-heating under multiaxial high cycle fatigue

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2010年第4期58卷 578-593页

作者： Poncelet, M. Doudard, C. Calloch, S. Weber, B. Hild, F. Univ Paris 11 PRES Univ Paris 06 LMT CachanENS CachanCNRS F-94235 Cachan France Univ Brest ENIB ENSIETA LBMS EA 4325 F-29806 Brest France ArcelorMittal Maizieres Res Voie Romaine F-57283 Maizieres Les Metz France

Different approaches have been proposed to link high cycle fatigue properties to thermal measurements under cyclic loadings, usually referred to as "self-heating tests." This paper focuses on two models whose parameters are tuned by resorting to self-heating tests and then used to predict high cycle fatigue properties. The first model is based upon a yield surface approach to account for stress multiaxiality at a microscopic scale, whereas the second one relies on a probabilistic modelling of microplasticity at the scale of slip-planes. Both model identifications are cost effective, relying mainly on quickly obtained temperature data in self-heating tests. They both describe the influence of the stress heterogeneity, the volume effect and the hydrostatic stress on fatigue limits. The thermal effects and mean fatigue limit predictions are in good agreement with experimental results for in and out-of phase tension-torsion loadings. In the case of fatigue under non-proportional loading paths, the mean fatigue limit prediction error of the critical shear stress approach is three times less than with the yield surface approach. (C) 2010 Elsevier Ltd. All rights reserved.

关键词： Thermomechanical process Metallic materials Mechanical testing probability and statistics Multiaxial fatigue

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Ductile-to-brittle transition in tensile failure of particle-reinforced metals

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2009年第3期57卷 473-499页

作者： Hauert, Aude Rossoll, Andreas Mortensen, Andreas Ecole Polytech Fed Lausanne Lab Mech Met Stn 12 CH-1015 Lausanne Switzerland

We present an analytical micromechanical model designed to simulate the tensile stress-strain behaviour and failure of damaging composites containing a high volume fraction of reinforcing particles. One internal damage micromechanism is considered, namely particle fracture, which is assumed to obey a Weibull distribution. Final composite tensile failure occurs when one of two possible failure criteria is reached, given by (i) the onset of tensile instability, or (ii) an "avalanche-like" propagation of particle breaks to neighbouring particles. We show that an experimentally observed transition from failure by tensile instability to abrupt failure resulting from an increase of matrix strength can be mimicked by the model because local load-sharing (i.e. load transfer from a broken particle to its immediate neighbours) is accounted for. (C) 2008 Elsevier Ltd. All rights reserved.

关键词： Particulate reinforced material Fracture mechanisms Internal damage Microcracking probability and statistics

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Boundary-layer corrections for stress and strain fields in randomly heterogeneous materials

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2003年第6期51卷 1075-1088页

作者： Luciano, R Willis, JR Ctr Math Sci Dept Appl Math & Theoret Phys Cambridge CB3 0WA England Univ Cassino DiMSAT I-03043 Cassino FR Italy

Boundary-layer effects on the effective response of fibre-reinforced media are analysed. The distribution of the fibres is assumed random. A methodology is presented for obtaining non-local effective constitutive operators in the vicinity of a boundary. These relate ensemble averaged stress to ensemble averaged strain. Operators are also developed which re-construct the local fields from their ensemble averages. These require information on the local configuration of the medium. Complete information is likely not to be available, but averages of these operators conditional upon any given local information generate corresponding conditional averages of the fields. Explicit implementation is performed within the framework of an approximation of Hashin-Shtrikman type. Two types of geometry are considered in examples: a half-space and a crack in an infinite heterogeneous medium. These are representative, asymptotically, of the field in the vicinity of any smooth boundary, and in the vicinity of a crack tip, respectively. Results have been obtained for the case of anti-plane deformation, realized by the imposition of either Dirichlet or Neumann conditions on the boundary;those for the Neumann condition are presented and discussed explicitly. The stresses in both fibre and matrix adjacent to a crack tip are shown to differ substantially from the values that would be predicted by ordinary homogenization. (C) 2003 Elsevier Science Ltd. All rights reserved.

关键词： microstructures constitutive behaviour inhomogeneous material probability and statistics

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Nonlinear time series modelling and prediction using Gaussian RBF network with evolutionary structure optimisation

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ELECTRONICS LETTERS 2001年第10期37卷 639-640页

作者： Hong, SG Oh, SK Kim, MS Lee, JJ Korea Adv Inst Sci & Technol Dept Elect Engn & Comp Sci Yusung Gu Taejon South Korea

An evolutionary structure optimisation method for the Gaussian radial basis function network is presented for modelling and predicting nonlinear time series. The generalisation performance is significantly improved wi... 详细信息

关键词： radial basis function networks Gaussian radial basis function network generalisation performance Neural nets (circuit implementations) Optimisation techniques evolutionary structure optimisation time series Neural computing techniques Gaussian RBF network nonlinear time series circuit optimisation nonlinear time series modelling probability and statistics clustering least square learning method

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COMPARISON OF 2 STATISTICAL TESTS FOR KEYSTREAM SEQUENCES

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ELECTRONICS LETTERS 1987年第8期23卷 365-366页

作者： KIMBERLEY, M Department of Mathematical Sciences Goldsmith's College London UK

The generalised serial test for keystream sequences is compared with the poker test. It is suggested that the generalised serial test should be used in preference to the poker test.

关键词： cryptography Codes statistical tests poker test keystream sequences encryption statistics binary stream cipher system probability and statistics codes generalised serial test

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