The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Laurent Krähenbühl - One of the best experts on this subject based on the ideXlab platform.
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Subproblem Methodology for Progressive Finite Element Modeling of Transformers
2015Co-Authors: Patrick Dular, Mauricio Ferreira Da Luz, Patrick Kuo-peng, Laurent KrähenbühlAbstract:Model refinements of transformers are performed via a Subproblem finite element method. A complete problem is split into Subproblems with overlapping meshes, to allow a progressive modeling from ideal to real flux tubes, 1-D to 2-D to 3-D models, linear to nonlinear materials, perfect to real materials, wired to volume inductors, and homogenized to fine models of cores and coils, with any coupling of these changes. Its solution is the sum of the Subproblem solutions. The procedure simplifies both meshing and solving processes, and quantifies the gain given by each refinement on both local fields and global quantities. Efficient ways to chain the refinements are proposed and tested.
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correction of homogenized lamination stacks via a Subproblem finite element method
16th IGTE, 2014Co-Authors: Patrick Dular, Patrick Kuopeng, Mauricio Valencia Ferreira Da Luz, Laurent KrähenbühlAbstract:Purpose – The purpose of this paper is to develop a Subproblem finite element method for progressive modeling of lamination stacks in magnetic cores, from homogenized solutions up to accurate eddy current distributions and losses. Design/methodology/approach – The homogenization of lamination stacks, subject to both longitudinal and transversal magnetic fluxes, is first performed and is followed by local correction Subproblems in certain laminations separately, surrounded by their insulating layers and the remaining laminations kept homogenized. The sources for the local corrections are originally defined via interface conditions to allow the coupling between homogenized and non-homogenized portions. Findings – The errors proper to the homogenization model, which neglects fringing effects, can be locally corrected in some selected portions via local eddy current Subproblems considering the actual geometries and properties of the related laminations. The fineness of the mesh can thus be concentrated in the...
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Progressive Source and Reaction Fields for Magnetodynamic Model Refinement via a Finite Element Subproblem Method
2014Co-Authors: Patrick Dular, Mauricio Ferreira Da Luz, Patrick Kuo-peng, Laurent KrähenbühlAbstract:Magnetodynamic models are split into a sequence of progressive finite element Subproblems. The source fields generated by the active conductors alone are calculated at first via either finite elements or the Biot-Savart law. The associated reaction fields for each added magnetic and/or conductingregion, and in return for the source regions themselves when massive, are then calculated with finite element models, possibly with initial perfect magnetic, conductor and/or impedance boundary conditions to be further corrected. The resulting Subproblem method allows efficient solving of parameterized analyses thanks to a proper mesh for each Subproblem and the reuse of previous solutions to be locally corrected. Accuracy improvements are obtained for local fields and global quantities, i.e. inductances, resistances, Joule losses and forces.
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Subproblem approach for modeling multiply connected thin regions with an h conformal magnetodynamic finite element formulation
European Physical Journal-applied Physics, 2013Co-Authors: Vuong Quoc Dang, Ruth Sabariego, Patrick Dular, Laurent Krähenbühl, Christophe GeuzaineAbstract:A Subproblem h-conform eddy current finite element method is proposed for correcting the inaccuracies inherent to thin shell models. Such models replace volume thin regions by surfaces but neglect border effects in the vicinity of their edges and corners. The developed surface-to-volume correction problem is defined as a step of the multiple Subproblems applied to a complete problem, consisting of inductors and magnetic or conducting regions, some of these being thin regions. The general case of multiply connected thin regions is considered.
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a finite element Subproblem method for position change conductor systems
IEEE Transactions on Magnetics, 2012Co-Authors: Patrick Dular, Ruth Sabariego, Laurent Krähenbühl, M V F Da Luz, Patrick Kuopeng, Christophe GeuzaineAbstract:Analyses of magnetic systems with position changes of both massive and stranded conductors are performed via a finite element Subproblem method. A complete problem is split into Subproblems associated with each conductor and the magnetic regions. Each complete solution is then expressed as the sum of Subproblem solutions supported by different meshes. The Subproblem procedure simplifies both meshing and solving processes, with no need of remeshing, and accurately quantifies the effect of the position changes of conductors on both local fields, e.g., skin and proximity effects, and global quantities, e.g., inductances and forces. Applications covering parameterized analyses on conductor positions to moving conductor systems can benefit from the developed approach.
Patrick Dular - One of the best experts on this subject based on the ideXlab platform.
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Subproblem Methodology for Progressive Finite Element Modeling of Transformers
2015Co-Authors: Patrick Dular, Mauricio Ferreira Da Luz, Patrick Kuo-peng, Laurent KrähenbühlAbstract:Model refinements of transformers are performed via a Subproblem finite element method. A complete problem is split into Subproblems with overlapping meshes, to allow a progressive modeling from ideal to real flux tubes, 1-D to 2-D to 3-D models, linear to nonlinear materials, perfect to real materials, wired to volume inductors, and homogenized to fine models of cores and coils, with any coupling of these changes. Its solution is the sum of the Subproblem solutions. The procedure simplifies both meshing and solving processes, and quantifies the gain given by each refinement on both local fields and global quantities. Efficient ways to chain the refinements are proposed and tested.
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correction of homogenized lamination stacks via a Subproblem finite element method
16th IGTE, 2014Co-Authors: Patrick Dular, Patrick Kuopeng, Mauricio Valencia Ferreira Da Luz, Laurent KrähenbühlAbstract:Purpose – The purpose of this paper is to develop a Subproblem finite element method for progressive modeling of lamination stacks in magnetic cores, from homogenized solutions up to accurate eddy current distributions and losses. Design/methodology/approach – The homogenization of lamination stacks, subject to both longitudinal and transversal magnetic fluxes, is first performed and is followed by local correction Subproblems in certain laminations separately, surrounded by their insulating layers and the remaining laminations kept homogenized. The sources for the local corrections are originally defined via interface conditions to allow the coupling between homogenized and non-homogenized portions. Findings – The errors proper to the homogenization model, which neglects fringing effects, can be locally corrected in some selected portions via local eddy current Subproblems considering the actual geometries and properties of the related laminations. The fineness of the mesh can thus be concentrated in the...
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Progressive Source and Reaction Fields for Magnetodynamic Model Refinement via a Finite Element Subproblem Method
2014Co-Authors: Patrick Dular, Mauricio Ferreira Da Luz, Patrick Kuo-peng, Laurent KrähenbühlAbstract:Magnetodynamic models are split into a sequence of progressive finite element Subproblems. The source fields generated by the active conductors alone are calculated at first via either finite elements or the Biot-Savart law. The associated reaction fields for each added magnetic and/or conductingregion, and in return for the source regions themselves when massive, are then calculated with finite element models, possibly with initial perfect magnetic, conductor and/or impedance boundary conditions to be further corrected. The resulting Subproblem method allows efficient solving of parameterized analyses thanks to a proper mesh for each Subproblem and the reuse of previous solutions to be locally corrected. Accuracy improvements are obtained for local fields and global quantities, i.e. inductances, resistances, Joule losses and forces.
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Subproblem approach for modeling multiply connected thin regions with an h conformal magnetodynamic finite element formulation
European Physical Journal-applied Physics, 2013Co-Authors: Vuong Quoc Dang, Ruth Sabariego, Patrick Dular, Laurent Krähenbühl, Christophe GeuzaineAbstract:A Subproblem h-conform eddy current finite element method is proposed for correcting the inaccuracies inherent to thin shell models. Such models replace volume thin regions by surfaces but neglect border effects in the vicinity of their edges and corners. The developed surface-to-volume correction problem is defined as a step of the multiple Subproblems applied to a complete problem, consisting of inductors and magnetic or conducting regions, some of these being thin regions. The general case of multiply connected thin regions is considered.
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a finite element Subproblem method for position change conductor systems
IEEE Transactions on Magnetics, 2012Co-Authors: Patrick Dular, Ruth Sabariego, Laurent Krähenbühl, M V F Da Luz, Patrick Kuopeng, Christophe GeuzaineAbstract:Analyses of magnetic systems with position changes of both massive and stranded conductors are performed via a finite element Subproblem method. A complete problem is split into Subproblems associated with each conductor and the magnetic regions. Each complete solution is then expressed as the sum of Subproblem solutions supported by different meshes. The Subproblem procedure simplifies both meshing and solving processes, with no need of remeshing, and accurately quantifies the effect of the position changes of conductors on both local fields, e.g., skin and proximity effects, and global quantities, e.g., inductances and forces. Applications covering parameterized analyses on conductor positions to moving conductor systems can benefit from the developed approach.
Panos Y Papalambros - One of the best experts on this subject based on the ideXlab platform.
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a sequential linear programming coordination algorithm for analytical target cascading
Design Automation Conference, 2007Co-Authors: Panos Y PapalambrosAbstract:Decomposition-based strategies, such as analytical target cascading (ATC), are often employed in design optimization of complex systems. Achieving convergence and computational efficiency in the coordination strategy that solves the partitioned problem is a key challenge. A new convergent strategy is proposed for ATC that coordinates interactions among Subproblems using sequential linearizations. The linearity of Subproblems is maintained using infinity norms to measure deviations between targets and responses. A Subproblem suspension strategy is used to suspend temporarily inclusion of Subproblems that do not need significant redesign, based on trust region and target value step size. An individual Subproblem trust region method is introduced for faster convergence. The proposed strategy is intended for use in design optimization problems where sequential linearizations are typically effective, such as problems with extensive monotonicities, a large number of constraints relative to variables, and propagation of probabilities with normal distributions. Experiments with test problems show that, relative to standard ATC coordination, the number of Subproblem evaluations is reduced considerably while the solution accuracy depends on the degree of monotonicity and nonlinearity.
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an augmented lagrangian relaxation for analytical target cascading using the alternating direction method of multipliers
Structural and Multidisciplinary Optimization, 2006Co-Authors: S Tosserams, Panos Y Papalambros, L F P Etman, J E RoodaAbstract:Analytical target cascading is a method for design optimization of hierarchical, multilevel systems. A quadratic penalty relaxation of the system consistency constraints is used to ensure Subproblem feasibility. A typical nested solution strategy consists of inner and outer loops. In the inner loop, the coupled Subproblems are solved iteratively with fixed penalty weights. After convergence of the inner loop, the outer loop updates the penalty weights. The article presents an augmented Lagrangian relaxation that reduces the computational cost associated with ill-conditioning of Subproblems in the inner loop. The alternating direction method of multipliers is used to update penalty parameters after a single inner loop iteration, so that Subproblems need to be solved only once. Experiments with four examples show that computational costs are decreased by orders of magnitude ranging between 10 and 1000.
Christophe Geuzaine - One of the best experts on this subject based on the ideXlab platform.
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two way coupling of thin shell finite element magnetic models via an iterative Subproblem method
Compel-the International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 2020Co-Authors: Vuong Quoc Dang, Christophe GeuzaineAbstract:The purpose of this paper is to deal with the correction of the inaccuracies near edges and corners arising from thin shell models by means of an iterative finite element Subproblem method. Classical thin shell approximations of conducting and/or magnetic regions replace the thin regions with impedance-type transmission conditions across surfaces, which introduce errors in the computation of the field distribution and Joule losses near edges and corners.,In the proposed approach local corrections around edges and corners are coupled to the thin shell models in an iterative procedure (each Subproblem being influenced by the others), allowing to combine the efficiency of the thin shell approach with the accuracy of the full modelling of edge and corner effects.,The method is based on a thin shell solution in a complete problem, where conductive thin regions have been extracted and replaced by surfaces but strongly neglect errors on computation of the field distribution and Joule losses near edges and corners.,This model is only limited to thin shell models by means of an iterative finite element Subproblem method.,The developed method is considered to couple Subproblems in two-way coupling correction, where each solution is influenced by all the others. This means that an iterative procedure between the Subproblems must be required to obtain an accurate (convergence) solution that defines as a series of corrections.
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Subproblem approach for modeling multiply connected thin regions with an h conformal magnetodynamic finite element formulation
European Physical Journal-applied Physics, 2013Co-Authors: Vuong Quoc Dang, Ruth Sabariego, Patrick Dular, Laurent Krähenbühl, Christophe GeuzaineAbstract:A Subproblem h-conform eddy current finite element method is proposed for correcting the inaccuracies inherent to thin shell models. Such models replace volume thin regions by surfaces but neglect border effects in the vicinity of their edges and corners. The developed surface-to-volume correction problem is defined as a step of the multiple Subproblems applied to a complete problem, consisting of inductors and magnetic or conducting regions, some of these being thin regions. The general case of multiply connected thin regions is considered.
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a finite element Subproblem method for position change conductor systems
IEEE Transactions on Magnetics, 2012Co-Authors: Patrick Dular, Ruth Sabariego, Laurent Krähenbühl, M V F Da Luz, Patrick Kuopeng, Christophe GeuzaineAbstract:Analyses of magnetic systems with position changes of both massive and stranded conductors are performed via a finite element Subproblem method. A complete problem is split into Subproblems associated with each conductor and the magnetic regions. Each complete solution is then expressed as the sum of Subproblem solutions supported by different meshes. The Subproblem procedure simplifies both meshing and solving processes, with no need of remeshing, and accurately quantifies the effect of the position changes of conductors on both local fields, e.g., skin and proximity effects, and global quantities, e.g., inductances and forces. Applications covering parameterized analyses on conductor positions to moving conductor systems can benefit from the developed approach.
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Subproblem finite element method for magnetic model refinements
ISEF, 2011Co-Authors: Patrick Dular, Ruth Sabariego, Laurent Krähenbühl, Patrick Kuopeng, Mauricio Ferreira V Da Luz, Christophe GeuzaineAbstract:Model refinements of magnetic circuits are performed via a Subproblem finite element method. A complete problem is split into Subproblems with overlapping meshes, to allow a progression from source to reaction fields, ideal to real flux tubes, 1-D to 2-D to 3-D models, perfect to real materials, with any coupling of these changes. Its solution is the sum of the Subproblem solutions. The procedure simplifies both meshing and solving processes, and quantifies the gain given by each refinement on both local fields and global quantities.
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Progressive eddy current modeling via a finite element Subproblem method
International Journal of Applied Electromagnetics and Mechanics, 2003Co-Authors: Patrick Dular, Laurent Krähenbühl, Victor Péron, Christophe GeuzaineAbstract:The modeling of eddy currents in conductors is split into a sequence of progressive finite element Subproblems. The source fields generated by the inductors alone are calculated at first via either the Biot-Savart law or finite elements. The associated reaction fields for each added conductive region, and in return for the source regions themselves when massive, are then calculated with finite element models, possibly with initial perfect conductor and/or impedance boundary conditions to be further corrected. The resulting Subproblem method allows efficient solving of parameterized analyses thanks to a proper mesh for each Subproblem and the reuse of previous solutions to be locally corrected.
Pitu B Mirchandani - One of the best experts on this subject based on the ideXlab platform.
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solving simultaneous route guidance and traffic signal optimization problem using space phase time hypernetwork
Transportation Research Part B-methodological, 2015Co-Authors: Pitu B Mirchandani, Xuesong ZhouAbstract:This paper addresses the problem of simultaneous route guidance and traffic signal optimization problem (RGTSO) where each vehicle in a traffic network is guided on a path and the traffic signals servicing these vehicles are set to minimize their travel times. The network is modeled as a space-phase-time (SPT) hyper-network to explicitly represent the traffic signal control phases and time-dependent vehicle paths. A Lagrangian-relaxation-based optimization framework is proposed to decouple the RGTSO problem into two Subproblems: the Route Guidance (RG) problem for multiple vehicles with given origins and destinations and the Traffic Signal Optimization (TSO) problem. In the RG Subproblem, the route of each vehicle is provided subject to time-dependent link capacities imposed by the solution of the TSO problem, while the traffic signal timings are optimized according to the respective link travel demands aggregated from the vehicle trajectories. The dual prices of the RG Subproblem indicate search directions for optimization of the traffic signal phase sequences and durations in the TSO Subproblem. Both RG and TSO Subproblems can be solved using a computationally efficient finite-horizon dynamic programming framework, enhanced by parallel computing techniques. Two numerical experiments demonstrated that the system optimum of the RGTSO problem can be quickly reached with relatively small duality gap for medium-size urban networks.
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a real time traffic signal control system architecture algorithms and analysis
Transportation Research Part C-emerging Technologies, 2001Co-Authors: Pitu B Mirchandani, Larry HeadAbstract:Abstract The paper discusses a real-time traffic-adaptive signal control system referred to as RHODES. The system takes as input detector data for real-time measurement of traffic flow, and “optimally” controls the flow through the network. The system utilizes a control architecture that (1) decomposes the traffic control problem into several Subproblems that are interconnected in an hierarchical fashion, (2) predicts traffic flows at appropriate resolution levels (individual vehicles and platoons) to enable pro-active control, (3) allows various optimization modules for solving the hierarchical Subproblems, and (4) utilizes a data structure and computer/communication approaches that allow for fast solution of the Subproblems, so that each decision can be downloaded in the field appropriately within the given rolling time horizon of the corresponding Subproblem. The RHODES architecture, algorithms, and its analysis are presented. Laboratory test results, based on implementation of RHODES on simulation models of actual scenarios, illustrate the effectiveness of the system.
