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ESTIMATION OF DELAYS AND OTHER PARAMETERS IN NON-LINEAR FUNCTIONAL-DIFFERENTIAL EQUATIONS

SIAM JOURNAL ON CONTROL AND OPTIMIZATION 1983年第6期21卷 895-915页

作者： BANKS, HT LAMM, PKD SO METHODIST UNIV DEPT MATHDALLASTX 75275 NASA LANGLEY RES CTRINST COMP APPLICAT SCI & ENGNHAMPTONVA 23665

We discuss a spline-based approximation scheme for nonlinear nonautonomous delay differential equations. Convergence results (using dissipative type estimates on the underlying nonlinear operators) are given in the context of parameter estimation problems which include estimation of multiple delays and initial data as well as the usual coefficient-type parameters. A brief summary of some of our related numerical findings is also given.

关键词： delay equations parameter estimation splines numerical algorithms

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SYSTEM PERFORMANCE AND EXECUTION OF SCIENTIFIC algorithms ON THE PARALLEL COMPUTER PARAWELL

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PARALLEL COMPUTING 1990年第2期13卷 159-173页

作者： ECKARDT, H Siemens AG Zentralabteilung Forschung und Entwicklung Dept. ZFE F 2 SYS 3 Otto-Hahn-Ring 6 D-8000 München 83 FRG

In this paper the architecture of the bus-connected, hierarchical parallel computer system Parawell used in the Siemens research laboratories in Munich is presented. Benchmark results testing the individual nodes and the Parawell bus are given. A general model for the speedup of parallel algorithms on the Parawell is discussed. For the implementation of several numerical algorithms (Fourier transformation, Laplace equation, N -body problem, systems of linear equations) the Parawell was proven to be suitable as long as the size of the individual tasks was sufficiently large.

关键词： benchmark results Computer system Parawell numerical algorithms system performance measurements

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DAMAGE EVOLUTION MODELING IN ORTHOTROPIC LAMINATED COMPOSITES

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AIAA JOURNAL 1994年第2期32卷 357-364页

作者： DZENIS, YA JOSHI, SP BOGDANOVICH, AE LATVIAN ACAD SCI CTR ENGN & TECHNOLRIGALATVIA

Composites have inherent scatter in elastic and strength properties. A probabilistic model utilizing random material characteristics to predict damage evolution in orthotropic laminated composites is presented in this paper. The proposed model is based on the division of laminated composites into a statistically large number of mesoelements (mesovolumes). The mesovolume is assumed to be large enough to be structurally homogeneous, and at the same time it has to be comparatively small to satisfy the condition of stochastic homogeneity of stress and strain fields. Three modes of mesovolume failure, i.e., fibre breakage and matrix failure in the transverse direction as well as matrix shear cracking, are taken into account. Damage formation in a ply and in a laminate as a whole for a given plane stress state is calculated from the probabilities of mesovolume failure. These probabilities are directly utilized in reducing ply material constants. A numerical algorithm for damage accumulation and deformation history predictions for orthotropic laminated composites are developed. The behavior of a laminated orthotropic composite is presented as an illustrative example. Analysis of angle-ply Kevlar/epoxy laminates subjected to tension, compression, and shear loading is performed. The effect of scatters in elastic and strength characteristics on damage evolution is shown.

关键词： Fiber Reinforced Composites Elastic Properties Plane Stress numerical algorithms Material Properties Cumulative Damage Quasistatic Loading Statistical Distributions Monte Carlo Simulation Quasistatic Process

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Zeroing neural networks: A survey

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NEUROCOMPUTING 2017年 267卷 597-604页

作者： Jin, Long Li, Shuai Liao, Bolin Zhang, Zhijun Lanzhou Univ Sch Informat Sci & Engn Lanzhou 730000 Gansu Peoples R China Hong Kong Polytech Univ Dept Comp Kowloon Hong Kong Peoples R China Jishou Univ Coll Informat Sci & Engn Jishou 416000 Peoples R China South China Univ Technol Sch Automat Sci & Engn Guangzhou 510640 Guangdong Peoples R China

Using neural networks to handle intractability problems and solve complex computation equations is becoming common practices in academia and industry. It has been shown that, although complicated, these problems can be formulated as a set of equations and the key is to find the zeros of them. Zeroing neural networks (ZNN), as a class of neural networks particularly dedicated to find zeros of equations, have played an indispensable role in the online solution of time-varying problem in the past years and many fruitful research outcomes have been reported in the literatures. The aim of this paper is to provide a comprehensive survey of the research on ZNN5, including continuous-time and discrete-time ZNN models for various problems solving as well as their applications in motion planning and control of redundant manipulators, tracking control of chaotic systems, or even populations control in mathematical biosciences. By considering the fact that real-time performance is highly demanded for time-varying problems in practice, stability and convergence analyses of different continuous-time ZNN models are reviewed in detail in a unified way. For the case of discrete-time problems solving, the procedures on how to discretize a continuous-time ZNN model and the techniques on how to obtain an accuracy solution are summarized. Concluding remarks and future directions of ZNN are pointed out and discussed. (C) 2017 Elsevier B.V. All rights reserved.

关键词： Zeroing neural network Recurrent neural network Stability numerical algorithms Redundant manipulators Robust stability

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Thermo-mechanical strain gradient plasticity with energetic and dissipative length scales

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INTERNATIONAL JOURNAL OF PLASTICITY 2012年 30-31卷 218-247页

作者： Voyiadjis, George Z. Faghihi, Danial Louisiana State Univ Dept Civil & Environm Engn Computat Solid Mech Lab Baton Rouge LA 70803 USA

Plasticity in heterogeneous metallic materials of small volumes is governed by the interactions of the dislocations in the bulk and at the interfaces. The temperature distribution and accumulated heat in the medium, due to the high rate of loading, can also strongly affect the mechanical properties in micro and nanosystems. In this paper, the framework of higher-order strain gradient plasticity with interfacial energy effect is used to investigate the coupling of thermal and mechanical responses of materials in small scales and fast transient process. In order to accurately describe the size effect exhibited in micro/nano structured materials and to address the strengthening and hardening mechanisms, the theory is developed based on the decomposition of the mechanical state variables into energetic and dissipative counterparts. This, in turn, endowed the constitutive equations to have both energetic and dissipative gradient length scales l(en) and l(dis) respectively. The effect of the material microstructural interface between two materials is also incorporated into the proposed formulation. Hence four material length scales are introduced: two for the bulk and the other two for the interface. In addition, the temperature distribution in the system due to conversion of plastic work into heat and the partial dissipation of heat due to fast transient time, is included into the model using a generalized heat equation. The microstructural interactions (i.e. photon-electron coupling) and the effect of fast transients is considered by incorporating two time scales into the heat equation. The developed framework is solved numerically by using a thin film on an elastic substrate under biaxial straining. Furthermore, the obtained results are compared with experimental data. (C) 2011 Elsevier Ltd. All rights reserved.

关键词： Thermomechanical processes Constitutive behaviour Viscoplastic material numerical algorithms Thin films

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Polynomial Shaping of the Look Angle for Impact-Time Control

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2017年第10期40卷 2668-2673页

作者： Tekin, Raziye Erer, Koray S. Holzapfel, Florian Aselsan Inc MGEO Nav & Guidance Syst Design Dept TR-06750 Ankara Turkey Roketsan Missiles Inc TMS Guidance Syst Design Dept TR-06780 Ankara Turkey Tech Univ Munich Inst Flight Syst Dynam D-85748 Munich Germany

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Dislocation glide in Fe-carbon solid solution: From atomistic to continuum level description

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INTERNATIONAL JOURNAL OF PLASTICITY 2014年第0期62卷 34-49页

作者： Khater, H. A. Monnet, G. Terentyev, D. Serra, A. Assiut Univ Dept Phys Fac Sci Assiut 71516 Egypt MMC EDF R&D F-77818 Moret Sur Loing France SMA NMS SCK CEN Struct Mat Modelling & Microstruct Unit B-2400 Mol Belgium Univ Politecn Cataluna ES-08034 Barcelona Spain

The role of interstitial carbon impurities on the dislocation glide in bcc iron is investigated by means of molecular dynamics simulations. The local stress induced by carbon atoms, interaction energy map for the a(0)/2 < 111 >{110} and a(0)/2 < 111 >{112} edge dislocations and the dynamics of dislocation carbon interaction is assessed. The local stress exerted on the dislocation due to the carbon atoms and computed by atomistic simulations is used to describe the interaction strength on the continuum level. The derived here analysis of the atomistic data enabled the determination of the activation enthalpy and volume as a function of stress. Having that information, a comparative study demonstrates that at finite temperature, the resistance to the dislocation glide induced by the carbon atoms is lower in {112} than in {110} slip systems. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Dislocations Impurities Strengthening mechanisms Crystal plasticity numerical algorithms

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Accuracy and coupling issues of aeroelastic navier-stokes solutions on deforming meshes

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JOURNAL OF AIRCRAFT 1998年第5期35卷 798-805页

作者： Morton, SA Melville, RB Visbal, MR USAF Res Lab Aeromech Div Wright Patterson AFB OH 45433 USA

An implicit time-accurate approach to aeroelastic simulation was developed with particular attention paid to the issues of time accuracy, structural coupling, grid-deformation strategy, and geometric conservation. A Beam-Warming, approximate-factored algorithm, modified to include Newton-like subiterations was coupled with a structural model, also in subiteration form. With a sufficient number of subiterations, this approach becomes a fully implicit, first- or second-order-accurate aeroelastic solver. The solver was used to compute time-accurate solutions of an elastically mounted cylinder. The fully implicit coupling allowed the overall scheme to become second-order accurate in time, significantly reducing the workload for a given accuracy. A new algebraic grid deformation strategy was developed that preserves grid orthogonality near the surface under large deformations. Finally, the oscillatory behavior of an elastically mounted cylinder was reproduced accurately by the present approach, and results compared favorably to previous experiments and simulations.

关键词： Structural Modeling Computing Time Freestream Mach Number Strouhal Number Structural Dynamics numerical Simulation Viscosity numerical algorithms Turbulence Models Angle of Attack

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INVISCID AND VISCOUS TRANSONIC-FLOWS IN CASCADES USING AN IMPLICIT UPWIND ALGORITHM

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JOURNAL OF PROPULSION AND POWER 1992年第2期8卷 403-409页

作者： BENETSCHIK, H GALLUS, HE Institut fur Strahlantriebe und Turboarbeitsmaschinen Aachen D-1500 Germany

This article presents a numerical algorithm for calculating inviscid and viscous flows in transonic and supersonic turbomachinery cascades. Of particular interest is the prediction of shock-induced boundary-layer separation and the comparison with experiments. The numerical procedure uses upwind-biased differencing with an approximate Riemann solver for the inviscid Euler fluxes. The viscous fluxes are discretized with careful treatment of cross derivatives. Convergence to a steady state is accelerated by use of an implicit relaxation strategy. The Baldwin-Lomax eddy-viscosity model is used for turbulent flows. Details of the numerical method are presented along with an appropriate grid generation procedure. Computed results show that the method can predict complicated viscous flow phenomena in cascades.

关键词： Compressible Flow Total Variation Diminishing Boundary Layer Separation Eddy Viscosity Supersonic Turbomachinery numerical algorithms Mach Numbers Reynolds Averaged Navier Stokes Bow Shock Turbomachinery Cascades

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THERMOCHEMICAL NONEQUILIBRIUM-FLOW COMPUTATIONS OF FLOW AROUND THE AEROASSIST FLIGHT EXPERIMENT

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 1992年第3期6卷 405-411页

作者： PALMER, G NASA AMES RES CTR AEROTHERMODYNAM BRANCH MOFFETT FIELD CA 94035 USA

A three-dimensional explicit, finite rate, shock-capturing, numerical algorithm is used to calculate thermochemical nonequilibrium flowfields about the Aeroassist Flight Experiment (AFE) vehicle at one or its flight trajectory points. The governing equations are expressed in cylindrical coordinates to alleviate perturbations in solution along the three-dimensional grid singular fine. The full Navier-Stokes equations and an 11-species chemical model with the latest reaction rates are incorporated into the code. Pressure, heat transfer, and temperature data are presented.

关键词： Nonequilibrium Flows Energy Exchange Mechanisms Navier Stokes Calculations Cylindrical Coordinate System Flight Trajectory numerical algorithms Conservation of Mass Vibrational Energy Shock Layers Conservation Equations

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