The Experts below are selected from a list of 147 Experts worldwide ranked by ideXlab platform
Wilfred F Van Gunsteren - One of the best experts on this subject based on the ideXlab platform.
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on using a too large Integration Time Step in molecular dynamics simulations of coarse grained molecular models
Physical Chemistry Chemical Physics, 2009Co-Authors: Moritz Winger, Daniel Trzesniak, Riccardo Baron, Wilfred F Van GunsterenAbstract:The use of a coarse-grained (CG) model that is widely used in molecular dynamics simulations of biomolecular systems is investigated with respect to the dependence of a variety of quantities upon the size of the used Integration Time Step and cutoff radius. The results suggest that when using a non-bonded interaction-cutoff radius of 1.4 nm a Time Step of maximally 10 fs should be used, in order not to produce energy sinks or wells. Using a too-large Time Step, e.g. 50 fs with a cutoff of 1.2 nm, as is done in the coarse-grained model of Marrink et al. (J. Phys. Chem. B, 2004, 108, 250 and 2007, 111, 7812), induces errors due to the linear approximation of the integrators that are commonly used to integrate the equations of motion. As a spin-off of the investigation of the mentioned CG models, we found that the parameters of the CG water model place it at physiological temperatures well into the solid phase of the phase diagram.
Thomas J. Overbye - One of the best experts on this subject based on the ideXlab platform.
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Optimal Subinterval Selection Approach for Power System Transient Stability Simulation
Energies, 2015Co-Authors: Soobae Kim, Thomas J. OverbyeAbstract:Power system transient stability analysis requires an appropriate Integration Time Step to avoid numerical instability as well as to reduce computational demands. For fast system dynamics, which vary more rapidly than what the Time Step covers, a fraction of the Time Step, called a subinterval, is used. However, the optimal value of this subinterval is not easily determined because the analysis of the system dynamics might be required. This selection is usually made from engineering experiences, and perhaps trial and error. This paper proposes an optimal subinterval selection approach for power system transient stability analysis, which is based on modal analysis using a single machine infinite bus (SMIB) system. Fast system dynamics are identified with the modal analysis and the SMIB system is used focusing on fast local modes. An appropriate subinterval Time Step from the proposed approach can reduce computational burden and achieve accurate simulation responses as well. The performance of the proposed method is demonstrated with the GSO 37-bus system.
Moritz Winger - One of the best experts on this subject based on the ideXlab platform.
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on using a too large Integration Time Step in molecular dynamics simulations of coarse grained molecular models
Physical Chemistry Chemical Physics, 2009Co-Authors: Moritz Winger, Daniel Trzesniak, Riccardo Baron, Wilfred F Van GunsterenAbstract:The use of a coarse-grained (CG) model that is widely used in molecular dynamics simulations of biomolecular systems is investigated with respect to the dependence of a variety of quantities upon the size of the used Integration Time Step and cutoff radius. The results suggest that when using a non-bonded interaction-cutoff radius of 1.4 nm a Time Step of maximally 10 fs should be used, in order not to produce energy sinks or wells. Using a too-large Time Step, e.g. 50 fs with a cutoff of 1.2 nm, as is done in the coarse-grained model of Marrink et al. (J. Phys. Chem. B, 2004, 108, 250 and 2007, 111, 7812), induces errors due to the linear approximation of the integrators that are commonly used to integrate the equations of motion. As a spin-off of the investigation of the mentioned CG models, we found that the parameters of the CG water model place it at physiological temperatures well into the solid phase of the phase diagram.
María Jesús Elejabarrieta - One of the best experts on this subject based on the ideXlab platform.
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finite element formulations for transient dynamic analysis in structural systems with viscoelastic treatments containing fractional derivative models
International Journal for Numerical Methods in Engineering, 2007Co-Authors: Fernando Cortés, María Jesús ElejabarrietaAbstract:This paper presents finite element formulations for transient dynamic analysis in structural systems with damping treatments in which viscoelastic materials are characterized by means of fractional derivative models. In contrast to other formulations, such as that of Padovan employing the principle of virtual work, the proposed formulations begin from the local equation of linear momentum and make use of the weighted residual method, providing a matrix equation of motion involving fractional operators. The numerical approximations of these are developed through the Grunwald–Letnikov definition, which allows to formulate explicit and implicit numerical schemes. The principal advantage of the proposed formulations is that the history of the displacements and external forces must be stored, but not that of the stress, which reduces computational Time and storage needs. Numerical applications are presented for a cantilever beam, where a viscoelastic treatment has been applied using damping material modelled by a five-parameter fractional derivative model. The results of the proposed formulation are compared among them and with those of Padovan for different damping values and for different load cases. The influence of the truncation of Grunwald coefficients and of the Integration Time-Step is also investigated. Copyright © 2006 John Wiley & Sons, Ltd.
Soobae Kim - One of the best experts on this subject based on the ideXlab platform.
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Optimal Subinterval Selection Approach for Power System Transient Stability Simulation
Energies, 2015Co-Authors: Soobae Kim, Thomas J. OverbyeAbstract:Power system transient stability analysis requires an appropriate Integration Time Step to avoid numerical instability as well as to reduce computational demands. For fast system dynamics, which vary more rapidly than what the Time Step covers, a fraction of the Time Step, called a subinterval, is used. However, the optimal value of this subinterval is not easily determined because the analysis of the system dynamics might be required. This selection is usually made from engineering experiences, and perhaps trial and error. This paper proposes an optimal subinterval selection approach for power system transient stability analysis, which is based on modal analysis using a single machine infinite bus (SMIB) system. Fast system dynamics are identified with the modal analysis and the SMIB system is used focusing on fast local modes. An appropriate subinterval Time Step from the proposed approach can reduce computational burden and achieve accurate simulation responses as well. The performance of the proposed method is demonstrated with the GSO 37-bus system.