Composite materials of two-dimensional structures are designed using the homogenization design method. The composite material is made of two or three different material phases. Designing the composite material consist...
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Composite materials of two-dimensional structures are designed using the homogenization design method. The composite material is made of two or three different material phases. Designing the composite material consists of finding a distribution of material phases that minimizes the mean compliance of the macrostructure subject to volume fraction constraints of the constituent phases, within a unit cell of periodic microstructures. At the start of the computational solution, the material distribution of the microstructure is represented as a pure mixture of the constituent phases. As the iteration procedure unfolds, the component phases separate themselves out to form distinctive interfaces. The effective material properties of the artificially mixed materials are defined by the interpolation of the constituents. The optimization problem is solved using the sequential linear programming method. Both the macrostructure and the microstructures are analysed using the finite element method in each iteration step. Several examples of optimal topology design of composite material are presented to demonstrate the validity of the present numerical algorithm. Copyright (C) 2001 John Wiley & Sons, Ltd.
An algorithm is proposed that enables fast generation of a trajectory that brings the state of a deficient satellite from a given initial position to the neighborhood of a final desired one. The proposed algorithm is ...
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An algorithm is proposed that enables fast generation of a trajectory that brings the state of a deficient satellite from a given initial position to the neighborhood of a final desired one. The proposed algorithm is then used to design a discrete sampling-based state feedback control. Finally, simulations are done to test the robustness of the closed loop behaviour against several configurations of uncertainties and disturbances.
A modified marine heat-flow probe has been proposed to conduct simultaneous measurements of thermal and electric properties of seafloor sediments. A major concern in the electric aspect is the shielding effect caused ...
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In order to investigate the dynamic characteristics of the AC induction motor hauling system more accurately, the mathematical models, which are used for digital simulation to the dynamic characteristics of rotating s...
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In order to investigate the dynamic characteristics of the AC induction motor hauling system more accurately, the mathematical models, which are used for digital simulation to the dynamic characteristics of rotating speed and torque are set up. The results show that the project is feasible and better than graphic solution.
A new algorithm is proposed to calculate the behavior of non-linear equations with multiple solutions. Use of this algorithm is demonstrated by calculation of compositions in an adsorbed layer for a vapor that exhibit...
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A new algorithm is proposed to calculate the behavior of non-linear equations with multiple solutions. Use of this algorithm is demonstrated by calculation of compositions in an adsorbed layer for a vapor that exhibits two-dimensional condensation. (C) 1998 Elsevier Science Ltd. All rights reserved.
A method to analyse bifurcation points by establishing bifurcation equations and solving them with an asymptotic expansion method is presented. Bifurcation equations are obtained using a decomposition of the spaces by...
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A method to analyse bifurcation points by establishing bifurcation equations and solving them with an asymptotic expansion method is presented. Bifurcation equations are obtained using a decomposition of the spaces by means of the theory of Lyapunov-Schmidt. To solve these bifurcation equations, an asymptotic expansion along the lines of Koiter is applied. The expansion is presented in a form suited for implementation in a finite element context. It is easy to extend the expansion to higher order terms in order to increase the accuracy. The accuracy of the method is verified with two examples. (C) 2000 Elsevier Science Ltd. All rights reserved.
Two stress fields, combination of total stresses, liquid pressure and gas pressure have to be considered to explain the deformational behaviour of unsaturated media. Elastoplastic models developed for. these materials...
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Two stress fields, combination of total stresses, liquid pressure and gas pressure have to be considered to explain the deformational behaviour of unsaturated media. Elastoplastic models developed for. these materials consider generally two yield surfaces, each one associated to a stress field, and whose intersection produces a corner in the space of generalised stress components. In this paper, a stress point algorithm is proposed to cope with the integration of such constitutive laws, which can be seen as non smooth multisurface plastic models in the space of the two stress fields. The basic model developed by Alonso et al. (Alonso, E.E., Gens, A., 1990. A constitutive model for partially saturated soils. Geotechnique 40 (3), 405-430), which will be used to test the algorithm, is first described. Generalised stress and strain variables are then defined. Implementation of the return mapping algorithm, based on an implicit integration scheme, is presented with special attention devoted to the problem of mixed control imposed by the F.E. formulation generally used to analyse the hydromechanical behaviour of unsaturated media. Validation results on distinct generalised stress paths are given at the end. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.
In the preceding companion paper (Bazant and Li, 1997), the solution of an aging viscoelastic structure containing a cohesive crack with a rate-dependent stress-displacement softening law was reduced to a system of on...
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In the preceding companion paper (Bazant and Li, 1997), the solution of an aging viscoelastic structure containing a cohesive crack with a rate-dependent stress-displacement softening law was reduced to a system of one-dimensional integro-differential equations involving compliance functions for points on the crack faces and the load point. An effective numerical algorithm for solving these equations, which dramatically reduces the computer time compared to the general two-dimensional finite element solution, is presented. The behavior of the model for various loading conditions is studied. It is shown that the model can closely reproduce the available experimental data from fracture tests with different loading rates spanning several orders of magnitude, and tests with sudden changes of the loading rate. Influence of the loading rate on the size effect and brittleness is also analyzed and is shown to agree with experiments.
This note describes a procedure for evaluating the accuracy of numerical solute transport models in situations where exact closed-form solutions are difficult or even impossible to obtain. The procedure attempts to ma...
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This note describes a procedure for evaluating the accuracy of numerical solute transport models in situations where exact closed-form solutions are difficult or even impossible to obtain. The procedure attempts to match a specified closed-form "test solution" by adding forcing terms to the original equation, which is solved numerically. The quality of the match provides valuable information about the performance of the numerical algorithm. We illustrate this "prescribed forcing method" with an example which simulates solute transport in a heterogeneous velocity field. The numerical solver considered in the example is based on the Eulerian-Lagrangian method with linear velocity and concentration interpolation. Two test solutions of different degrees of difficulty are considered. Differences between the exact and numerical test solutions for the example clearly reveal the influence of grid resolution on model accuracy. The example demonstrates that the prescribed forcing method can be used to assess numerical accuracy in practical situations where model inputs are highly variable and the true solution is unknown.
Application of genetic algorithms to texture analysis is presented in this paper. The genetic algorithm technique was applied to the calculation of the orientation distribution function from a set of pole figures. The...
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Application of genetic algorithms to texture analysis is presented in this paper. The genetic algorithm technique was applied to the calculation of the orientation distribution function from a set of pole figures. The results are very satisfying. The same algorithm may be also applied to other problems of texture analysis, e.g., to find an optimal texture for a given application.
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