The Experts below are selected from a list of 48330 Experts worldwide ranked by ideXlab platform

Alejandro Garces - One of the best experts on this subject based on the ideXlab platform.

  • On Convergence of Newtons Method in Power Flow Study for DC Microgrids
    IEEE Transactions on Power Systems, 2018
    Co-Authors: Alejandro Garces
    Abstract:

    The power flow is a non-linear problem that requires a Newton's Method to be solved in dc microgrids with constant power terminals. This paper presents sufficient conditions for the quadratic convergence of the Newton's Method in this type of grids. The classic Newton Method as well as an approximated Newton Method are analyzed in both master-slave and island operation with droop controls. Requirements for the convergence as well as for the existence and uniqueness of the solution starting from voltages close to 1pu are presented. Computational results complement this theoretical analysis.

Xi Dai - One of the best experts on this subject based on the ideXlab platform.

  • Implementation of LDA+Gutzwiller with Newtons Method*
    Chinese Physics B, 2017
    Co-Authors: Jian Zhang, Ming-feng Tian, Guang-xi Jin, Xi Dai
    Abstract:

    In order to calculate the electronic structure of correlated materials, we propose implementation of the LDA+Gutzwiller Method with Newton's Method. The self-consistence process, efficiency and convergence of calculation are improved dramatically by using Newton's Method with golden section search and other improvement approaches. We compare the calculated results by applying the previous linear mix Method and Newton's Method. We have applied our code to study the electronic structure of several typical strong correlated materials, including SrVO3, LaCoO3, and La2O3Fe2Se2. Our results fit quite well with the previous studies.

  • implementation of lda gutzwiller with Newtons Method
    Chinese Physics B, 2017
    Co-Authors: Jian Zhang, Ming-feng Tian, Guang-xi Jin, Xi Dai
    Abstract:

    In order to calculate the electronic structure of correlated materials, we propose implementation of the LDA+Gutzwiller Method with Newton's Method. The self-consistence process, efficiency and convergence of calculation are improved dramatically by using Newton's Method with golden section search and other improvement approaches. We compare the calculated results by applying the previous linear mix Method and Newton's Method. We have applied our code to study the electronic structure of several typical strong correlated materials, including SrVO3, LaCoO3, and La2O3Fe2Se2. Our results fit quite well with the previous studies.

R. Mahnken - One of the best experts on this subject based on the ideXlab platform.

  • A Newton-Multigrid algrithm for elasto-plastic/viscoplastic problems
    Computational Mechanics, 1995
    Co-Authors: R. Mahnken
    Abstract:

    This work is concerned with large scaled nonlinear systems of equations resulting from discretization of problems in plasticity and viscoplasticity in the context of the finite element Method. The main purpose is to show, how standard linear multigrid Methods can be applied for solving the associated linear systems of equations in the frame of the Newton-algorithm. To this end, a so-called Galerkin-approach is used for construction of coarse grid matrices by transformation of fine grid matrices. It will be shown, how this transformation can be performed very efficiently element-by-element wise. Stopping criteria for the inner iteration are based on theories for so-called inexact Newton Methods, where the linear systems are only solved approximately, however which preserve the rapid local convergence of Newtons Method. In the numerical examples it is demonstrated, how the proposed strategy reduces the CPU-time for large scaled problems compared to solution techniques, where the associated systems of linear equations are solved directly.

P W Selent - One of the best experts on this subject based on the ideXlab platform.

  • multiphase power flow solutions using emtp and Newtons Method
    IEEE Transactions on Power Systems, 1993
    Co-Authors: J J Allemong, R J Bennon, P W Selent
    Abstract:

    This paper describes a reliable and very flexible multiphase load-flow solution process which is applicable for large transmission systems (up to 500 nodes). The process consists of an interface between the Electromagnetic Transients Program (EMTP) and a newly developed multiphase load flow algorithm that is based on the Newton-Raphson Method. Subjects discussed include derivation of the basic algorithm, structure of the Jacobian matrix, and convergence characteristics. >

Niclas Strömberg - One of the best experts on this subject based on the ideXlab platform.

  • Topology Optimization of Orthotropic Elastic Design Domains with Mortar Contact Conditions
    Advances in Structural and Multidisciplinary Optimization, 2017
    Co-Authors: Niclas Strömberg
    Abstract:

    In this paper we perform topology optimization of orthotropic elastic design domains in unilateral contact with non-matching meshes by adopting the mortar approach. The motivation is 3D printing of assemblies of parts, where the build direction as well as the contact interfaces between the parts strongly will influence the optimal solutions. Thus, topology optimization of a standard isotropic formulation with tied interfaces might not be a proper approach for this kind of design problems. This is studied in this work by maximizing the potential energy of orthotropic linear elastic bodies in unilateral frictionless contact. In such manner, no extra adjoint equation is needed to be solved and non-zero prescribed displacements are also included in the formulation properly. This will not be true if the compliance is minimized. The contact conditions of the non-matching meshes are treated by deriving the mortar integral from the principle of virtual power by representing the normal contact pressure with the trace of the global displacement shape functions. The mortar integral is then approximated with the Lobatto rule using a high number of integration points. In such manner, we obtain a set of Signorini conditions for each non-matching interface which we solve using the augmented Lagrangian approach and Newtons Method. The design domains are formulated with orthotropic linear elasticity where intermediate density values are penalized using SIMP or RAMP, and the regularization is obtained by applying sensitivity or density filters following the approaches of Sigmund and Bourdin. The implementation of the Methodology is efficient and produces reliable solutions. This is demonstrated for assemblies of design domains in unilateral contact which is rotated with respect to the build direction of a 3D printer. In particular, compliance as function of build direction is generated for different problems. This kind of curves might be most useful when orienting the parts in order to minimize the volume of support structures.