miércoles, 14 de octubre de 2009

Comments on 'An efficient iterative method for solving the matrix equation AXB+CYD=E'


In this note, a technical error is pointed out in the proof of a lemma in the above paper. A correct proof of this lemma is given. In addition, a further result on the algorithm in the above paper is also given. Copyright © 2009 John Wiley & Sons, Ltd.



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Original source : http://dx.doi.org/10.1002%2Fnla.675...

Discrete element modeling of direct shear tests for a granular material


A succinct 3D discrete element model, with clumps to resemble the real shapes of granular materials, is developed. The quaternion method is introduced to transform the motion and force of a clump between local and global coordinates. The Hertz-Mindlin elastic contact force model, incorporated with the nonlinear normal viscous force and the Mohr-Coulomb friction law, is used to describe the interactions between particles. The proposed discrete element model is used to simulate direct shear tests of the irregular limestone rubbles. The simulation results of vertical displacements and shear stresses with a mixture of clumps are compared well with that of laboratory tests. The bulk friction coefficients are calculated and discussed under different contact friction coefficients and normal stresses. Copyright © 2009 John Wiley & Sons, Ltd.



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Original source : http://dx.doi.org/10.1002%2Fnag.848...