505,137 research outputs found
Flatness-based Deformation Control of an Euler-Bernoulli Beam with In-domain Actuation
This paper addresses the problem of deformation control of an Euler-Bernoulli
beam with in-domain actuation. The proposed control scheme consists in first
relating the system model described by an inhomogeneous partial differential
equation to a target system under a standard boundary control form. Then, a
combination of closed-loop feedback control and flatness-based motion planning
is used for stabilizing the closed-loop system around reference trajectories.
The validity of the proposed method is assessed through well-posedness and
stability analysis of the considered systems. The performance of the developed
control scheme is demonstrated through numerical simulations of a
representative micro-beam.Comment: Preprint of an original research wor
Direct simulation Monte Carlo schemes for Coulomb interactions in plasmas
We consider the development of Monte Carlo schemes for molecules with Coulomb
interactions. We generalize the classic algorithms of Bird and Nanbu-Babovsky
for rarefied gas dynamics to the Coulomb case thanks to the approximation
introduced by Bobylev and Nanbu (Theory of collision algorithms for gases and
plasmas based on the Boltzmann equation and the Landau-Fokker-Planck equation,
Physical Review E, Vol. 61, 2000). Thus, instead of considering the original
Boltzmann collision operator, the schemes are constructed through the use of an
approximated Boltzmann operator. With the above choice larger time steps are
possible in simulations; moreover the expensive acceptance-rejection procedure
for collisions is avoided and every particle collides. Error analysis and
comparisons with the original Bobylev-Nanbu (BN) scheme are performed. The
numerical results show agreement with the theoretical convergence rate of the
approximated Boltzmann operator and the better performance of Bird-type schemes
with respect to the original scheme
Finite Volume Streaming-based Lattice Boltzmann algorithm for fluid-dynamics simulations: a one-to-one accuracy and performance study
A new finite volume (FV) discretisation method for the Lattice Boltzmann (LB)
equation which combines high accuracy with limited computational cost is
presented. In order to assess the performance of the FV method we carry out a
systematic comparison, focused on accuracy and computational performances, with
the standard (ST) Lattice Boltzmann equation algorithm. To our
knowledge such a systematic comparison has never been previously reported. In
particular we aim at clarifying whether and in which conditions the proposed
algorithm, and more generally any FV algorithm, can be taken as the method of
choice in fluid-dynamics LB simulations. For this reason the comparative
analysis is further extended to the case of realistic flows, in particular
thermally driven flows in turbulent conditions. We report the first successful
simulation of high-Rayleigh number convective flow performed by a Lattice
Boltzmann FV based algorithm with wall grid refinement.Comment: 15 pages, 14 figures (discussion changes, improved figure
readability
IGS: an IsoGeometric approach for Smoothing on surfaces
We propose an Isogeometric approach for smoothing on surfaces, namely
estimating a function starting from noisy and discrete measurements. More
precisely, we aim at estimating functions lying on a surface represented by
NURBS, which are geometrical representations commonly used in industrial
applications. The estimation is based on the minimization of a penalized
least-square functional. The latter is equivalent to solve a 4th-order Partial
Differential Equation (PDE). In this context, we use Isogeometric Analysis
(IGA) for the numerical approximation of such surface PDE, leading to an
IsoGeometric Smoothing (IGS) method for fitting data spatially distributed on a
surface. Indeed, IGA facilitates encapsulating the exact geometrical
representation of the surface in the analysis and also allows the use of at
least globally continuous NURBS basis functions for which the 4th-order
PDE can be solved using the standard Galerkin method. We show the performance
of the proposed IGS method by means of numerical simulations and we apply it to
the estimation of the pressure coefficient, and associated aerodynamic force on
a winglet of the SOAR space shuttle
A Deterministic Model for Analyzing the Dynamics of Ant System Algorithm and Performance Amelioration through a New Pheromone Deposition Approach
Ant Colony Optimization (ACO) is a metaheuristic for solving difficult
discrete optimization problems. This paper presents a deterministic model based
on differential equation to analyze the dynamics of basic Ant System algorithm.
Traditionally, the deposition of pheromone on different parts of the tour of a
particular ant is always kept unvarying. Thus the pheromone concentration
remains uniform throughout the entire path of an ant. This article introduces
an exponentially increasing pheromone deposition approach by artificial ants to
improve the performance of basic Ant System algorithm. The idea here is to
introduce an additional attracting force to guide the ants towards destination
more easily by constructing an artificial potential field identified by
increasing pheromone concentration towards the goal. Apart from carrying out
analysis of Ant System dynamics with both traditional and the newly proposed
deposition rules, the paper presents an exhaustive set of experiments performed
to find out suitable parameter ranges for best performance of Ant System with
the proposed deposition approach. Simulations reveal that the proposed
deposition rule outperforms the traditional one by a large extent both in terms
of solution quality and algorithm convergence. Thus, the contributions of the
article can be presented as follows: i) it introduces differential equation and
explores a novel method of analyzing the dynamics of ant system algorithms, ii)
it initiates an exponentially increasing pheromone deposition approach by
artificial ants to improve the performance of algorithm in terms of solution
quality and convergence time, iii) exhaustive experimentation performed
facilitates the discovery of an algebraic relationship between the parameter
set of the algorithm and feature of the problem environment.Comment: 4th IEEE International Conference on Information and Automation for
Sustainability, 200
Mancha3D code: Multi-purpose Advanced Non-ideal MHD Code for High resolution simulations in Astrophysics
The Mancha3D code is a versatile tool for numerical simulations of
magnetohydrodynamic processes in solar/stellar atmospheres. The code includes
non-ideal physics derived from plasma partial ionization, a realistic equation
of state and radiative transfer, which allows performing high quality realistic
simulations of magneto-convection, as well as idealized simulations of
particular processes, such as wave propagation, instabilities or energetic
events. The paper summarizes the equations and methods used in the Mancha3D
code. It also describes its numerical stability and parallel performance and
efficiency. The code is based on a finite difference discretization and
memory-saving Runge-Kutta (RK) scheme. It handles non-ideal effects through
super-time stepping and Hall diffusion schemes, and takes into account thermal
conduction by solving an additional hyperbolic equation for the heat flux. The
code is easily configurable to perform different kinds of simulations. Several
examples of the code usage are given. It is demonstrated that splitting
variables into equilibrium and perturbation parts is essential for simulations
of wave propagation in a static background. A perfectly matched layer (PML)
boundary condition built into the code greatly facilitates a non-reflective
open boundary implementation. Spatial filtering is an important numerical
remedy to eliminate grid-size perturbations enhancing the code stability.
Parallel performance analysis reveals that the code is strongly memory bound,
which is a natural consequence of the numerical techniques used, such as split
variables and PML boundary conditions. Both strong and weak scalings show
adequate performance up till several thousands of CPUs
Implementation of Arithmetic Mean Method on Determination of Peak Junction Temperature of Semiconductor Device on Printed Circuit Board
High reliability users of microelectronic devices have been derating junction temperature and other critical stress parameters to improve device reliability and extend operating life. The junction temperature is what really matters for component functionality and reliability. This study presents a useful analysis on mathematical approach which can be implemented to predict thermal behavior in Integrated Circuit (IC). The problem could be modeled as heat conduction equation. In this study, numerical approaches based on implicit scheme and Arithmetic Mean (AM) iterative method will be applied to solve the governing heat conduction equation. From the numerical results obtained, it shows that AM method solves the governing heat conduction equation with minimum number of iterations and fastest computational time compared to the Gauss-Seidel (GS) method. It is in design phase when simulations and modeling are carried out to ensure high performance and reliability. The availability of thermal analysis tool for maximum temperature prediction would be of great value to designers of power device ICs
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