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Guest editorial
Engineering Analysis with Boundary Elements 19 (1997) 179 © 1997 Elsevier Science Limited All rights reserved. Printed in Great Britain ELSEVIER
Guest editorial This special issue of Engineering Analysis with Boundary Elements is focused on BEM/BIE approach for analysis of uncertain structures and physical phenomena. The nature of uncertainty can be discussed under: stochastic uncertainty and fuzzy uncertainty. The prediction of these types of uncertainty is difficult and present methods tend to concentrate on random uncertainty. There is, however, a fundamental difference between the nature of stochastic uncertainty and fuzzy uncertainty. The stochastic boundary element method (SBEM) belongs to computer methods which account for stochastic uncertainties in boundary conditions, material properties and geometry of the boundary. But if the underlying structure is not probabilistic, e.g. because of subjective choices, then it may be appropriate to use fuzzy numbers instead of real random variables. This leads to a fuzzy boundary-vale problem and in
consequence the fuzzy boundary element method (FBEM). The goal of this issue is to present new trends in computational methodology and applications to time-dependent (evolutional and dynamic) problems, random media, stochastic geometry and fuzzy aspects of BEM. Stochastic and fuzzy problems are, as a general rule, more computationally time-consuming and burdensome than deterministic problems. The SBEM and FBEM, which reduce the size of the problem by one and require solution only for stochastic or fuzzy boundary variables, appear-promising in various uncertain problems and belong to the rapidly advancing fields of computational mechanics. The guest editors are grateful to all authors for their excellent contributions. T. Burczy6ski A.H.-D. Cheng
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Guest editorial This special issue of Engineering Analysis with Boundary Elements is focused on BEM/BIE approach for analysis of uncertain structures and physical phenomena. The nature of uncertainty can be discussed under: stochastic uncertainty and fuzzy uncertainty. The prediction of these types of uncertainty is difficult and present methods tend to concentrate on random uncertainty. There is, however, a fundamental difference between the nature of stochastic uncertainty and fuzzy uncertainty. The stochastic boundary element method (SBEM) belongs to computer methods which account for stochastic uncertainties in boundary conditions, material properties and geometry of the boundary. But if the underlying structure is not probabilistic, e.g. because of subjective choices, then it may be appropriate to use fuzzy numbers instead of real random variables. This leads to a fuzzy boundary-vale problem and in
consequence the fuzzy boundary element method (FBEM). The goal of this issue is to present new trends in computational methodology and applications to time-dependent (evolutional and dynamic) problems, random media, stochastic geometry and fuzzy aspects of BEM. Stochastic and fuzzy problems are, as a general rule, more computationally time-consuming and burdensome than deterministic problems. The SBEM and FBEM, which reduce the size of the problem by one and require solution only for stochastic or fuzzy boundary variables, appear-promising in various uncertain problems and belong to the rapidly advancing fields of computational mechanics. The guest editors are grateful to all authors for their excellent contributions. T. Burczy6ski A.H.-D. Cheng
179