The Experts below are selected from a list of 30 Experts worldwide ranked by ideXlab platform
Rodrigo Rossi - One of the best experts on this subject based on the ideXlab platform.
-
A modified element-free Galerkin method with essential boundary conditions enforced by an Extended Partition of unity finite element weight function
International Journal for Numerical Methods in Engineering, 2003Co-Authors: Marcelo Krajnc Alves, Rodrigo RossiAbstract:In this work we propose a method which combines the element-free Galerkin (EFG) with an Extended Partition of unity finite element method (PUFEM), that is able to enforce, in some limiting sense, the essential boundary conditions as done in the finite element method (FEM). The proposed Extended PUFEM is based on the moving least square approximation (MLSA) and is capable of overcoming singularity problems, in the global shape functions, resulting from the consideration of linear and higher order base functions. With the objective of avoiding the presence of singular points, the Extended PUFEM considers an extension of the support of the classical PUFE weight function. Since the Extended PUFEM is closely related to the EFG method there is no need for special approximation functions with complex implementation procedures, and no use of the penalty and/or multiplier method is required in order to approximately impose the essential boundary condition. Thus, a relatively simple procedure is needed to combine both methods. In order to attest the performance of the method we consider the solution of an analytical elastic problem and also some coupled elastoplastic-damage problems. Copyright © 2003 John Wiley & Sons, Ltd.
Marcelo Krajnc Alves - One of the best experts on this subject based on the ideXlab platform.
-
A modified element-free Galerkin method with essential boundary conditions enforced by an Extended Partition of unity finite element weight function
International Journal for Numerical Methods in Engineering, 2003Co-Authors: Marcelo Krajnc Alves, Rodrigo RossiAbstract:In this work we propose a method which combines the element-free Galerkin (EFG) with an Extended Partition of unity finite element method (PUFEM), that is able to enforce, in some limiting sense, the essential boundary conditions as done in the finite element method (FEM). The proposed Extended PUFEM is based on the moving least square approximation (MLSA) and is capable of overcoming singularity problems, in the global shape functions, resulting from the consideration of linear and higher order base functions. With the objective of avoiding the presence of singular points, the Extended PUFEM considers an extension of the support of the classical PUFE weight function. Since the Extended PUFEM is closely related to the EFG method there is no need for special approximation functions with complex implementation procedures, and no use of the penalty and/or multiplier method is required in order to approximately impose the essential boundary condition. Thus, a relatively simple procedure is needed to combine both methods. In order to attest the performance of the method we consider the solution of an analytical elastic problem and also some coupled elastoplastic-damage problems. Copyright © 2003 John Wiley & Sons, Ltd.
Steven J Rowland - One of the best experts on this subject based on the ideXlab platform.
-
the Partition of fluoranthene and pyrene between suspended particles and dissolved phase in the humber estuary a study of the controlling factors
Science of The Total Environment, 1999Co-Authors: John L Zhou, T W Fileman, S V Evans, P Donkin, James W Readman, R F C Mantoura, Steven J RowlandAbstract:Abstract Particle–water interactions are one of the most important mechanisms controlling the distribution and movement of hydrophobic organic chemicals such as polycyclic aromatic hydrocarbons (PAHs) in aquatic environments (e.g. estuaries and oceans). To accurately predict the transport and fates of hydrophobic contaminants in estuarine and coastal marine environments, the Partition coefficient ( K p ) and organic carbon normalised Partition coefficient ( K oc ) are widely used in various biogeochemical models. Such Partition coefficients may be calculated from the so-called linear free energy relationships between K p , K oc and more easily measured parameters such as the octanol-water Partition coefficient ( K ow ). However K p and K oc values measured for real environmental samples of water and particles obtained from seasonal field surveys in the Humber Estuary, UK deviated from such ideals. For example, K P values showed no correlation with the fraction organic carbon content of particles ( f oc ) and instead of being constant, K oc , values varied with f oc . Both K p and K oc were 1–3 orders of magnitude higher than those predicted from the simple equilibrium–Partitioning model, but were in good agreement with several other recently published field studies. To improve our understanding of PAH Partitioning, the soot carbon (SC) content of particulate samples was measured so that the simple Partition model can be Extended to incorporate SC. The Partition coefficients derived from the Extended Partition model are very close to the field K p s. The results suggest that PAHs associated with particles are in fact present in the form of soot and soot-like particles that are not subject to particle–water equilibrations. In other words, the PAHs on soot-like particles are extremely strongly bound and not influenced by further Partitioning between the particles and water. However, there are still limitations with the Extended Partition model as it failed to simulate the field K oc values. No correlation was found between the Partition coefficients and salinity, which again we attribute to the non-equilibrium nature of the PAHs. However both K p and K oc generally decreased with increasing suspended solids concentrations (SSC) in the estuary. Such a relationship is probably due to the mixing of soot-like permanently suspended particles with resuspended estuarine sedimentary particles at the higher SSC values, and to the increased concentrations of dissolved organic carbon (DOC) associated with increase in SSC. However, it has been shown that DOC concentrations are not a suitable tool for correcting the SSC effect. There is therefore an urgent need to harmonise the laboratory and field approaches for K p measurements.
Yun Zhang - One of the best experts on this subject based on the ideXlab platform.
-
novel adaptive control design for nonlinear system with Extended Partition of unity method
Asian Journal of Control, 2013Co-Authors: Liang Luo, Yinhe Wang, Yongqing Fan, Yun ZhangAbstract:One of the amazing abilities of fuzzy logic systems or neural networks is their ability to approximate unknown certainties. When nonlinear systems possess multiple variables, however, the process of the adaptive fuzzy or neural network online control becomes difficult. In this paper, we will introduce the Extended Partition of unity (EPU), composed of scalars and saturators, to address this problem. The merit of the suggested design scheme is that the construction of the Partition of unity and the design of adaptive laws are separate. This means the proposed design method only adjusts the outputs of EPU and one update law, even in nonlinear systems with multiple variables. Therefore, this new method of EPU leads to easier selection of basis functions, reduces the number of adaptive laws, has greater robustness, and is suitable for different kinds of universal approximators. Finally, a numerical example is given to illustrate the effectiveness of the approach.
Inigo Perona - One of the best experts on this subject based on the ideXlab platform.
-
sep cop an efficient method to find the best Partition in hierarchical clustering based on a new cluster validity index
Pattern Recognition, 2010Co-Authors: Ibai Gurrutxaga, Inaki Albisua, Olatz Arbelaitz, Jose I Martin, Javier Muguerza, Jesus M Perez, Inigo PeronaAbstract:Hierarchical clustering algorithms provide a set of nested Partitions called a cluster hierarchy. Since the hierarchy is usually too complex it is reduced to a single Partition by using cluster validity indices. We show that the classical method is often not useful and we propose SEP, a new method that efficiently searches in an Extended Partition set. Furthermore, we propose a new cluster validity index, COP, since many of the commonly used indices cannot be used with SEP. Experiments performed with 80 synthetic and 7 real datasets confirm that SEP/COP is superior to the method currently used and furthermore, it is less sensitive to noise.
