6 results
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2. Hybrid Monte Carlo implementation of the Fourier path integral algorithm.
- Author
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Chakravarty, Charusita
- Subjects
- *
ALGORITHMS , *FOUNDATIONS of arithmetic , *MONTE Carlo method , *MATHEMATICAL models , *NUMERICAL analysis , *NUMERICAL calculations - Abstract
This paper formulates a hybrid Monte Carlo implementation of the Fourier path integral (FPI-HMC) approach with partial averaging. Such a hybrid Monte Carlo approach allows one to generate collective moves through configuration space using molecular dynamics while retaining the computational advantages associated with the Fourier path integral Monte Carlo method. In comparison with the earlier Metropolis Monte Carlo implementations of the FPI algorithm, the present HMC method is shown to be significantly more efficient for quantum Lennard-Jones solids and suggests that such algorithms may prove useful for efficient simulations of a range of atomic and molecular systems. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
3. Stochastic potential switching algorithm for Monte Carlo simulations of complex systems.
- Author
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Mak, C. H.
- Subjects
- *
MONTE Carlo method , *ALGORITHMS , *PROBABILITY theory , *STATISTICAL sampling , *NUMERICAL analysis , *MATHEMATICAL models , *ESTIMATION theory - Abstract
This paper describes a new Monte Carlo method based on a novel stochastic potential switching algorithm. This algorithm enables the equilibrium properties of a system with potential V to be computed using a Monte Carlo simulation for a system with a possibly less complex stochastically altered potential V. By proper choices of the stochastic switching and transition probabilities, it is shown that detailed balance can be strictly maintained with respect to the original potential V. The validity of the method is illustrated with a simple one-dimensional example. The method is then generalized to multidimensional systems with any additive potential, providing a framework for the design of more efficient algorithms to simulate complex systems. A near-critical Lennard-Jones fluid with more than 20 000 particles is used to illustrate the method. The new algorithm produced a much smaller dynamic scaling exponent compared to the Metropolis method and improved sampling efficiency by over an order of magnitude. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
4. Numerical modeling of Kelvin-Helmholtz instability by using potential equation.
- Author
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Ahmadi, Somayeh
- Subjects
- *
NUMERICAL analysis , *MATHEMATICAL models , *INCOMPRESSIBLE flow , *TWO-phase flow , *FLUID dynamics , *SHEAR flow , *ALGORITHMS - Abstract
This paper presents a potential flow numerical solution for the Kelvin-Helmholtz Instability (KHI) problem of an incompressible two-phase immiscible fluid in a stratified shear flow. As a problem: the two-fluid model becomes illposed when the slip velocity exceeds a critical value, and computations can be quite unstable before the flow reaches the ill-posed condition. In this work, computational stability of various convection schemes together with the potential equation method for the time derivatives in conjunction with the two-fluid model is analyzed. The normal stress balance (with the normal viscous stress) at the interface for the two-fluid model is carefully implemented to minimize its effect on numerical stability. Von Neumann stability analysis shows that: stability condition for two-fluid with equal kinematic viscosity ratio and inviscid flow, supply numerical stability. Excellent agreement has obtained according to analytical result that existing of imaginary part in solution which specialized this method. The numerical algorithm presented in this work can easily handle two-phase fluid flow with various density and viscosity ratios in rectangular channel. Simulation of this model has implemented by writing a code in FORTRAN programming. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
5. Four-stage computational technology with adaptive numerical methods for computational aerodynamics.
- Author
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Shaydurov, V., Liu, T., and Zheng, Z.
- Subjects
- *
NUMERICAL analysis , *ADAPTIVE control systems , *COMPUTATIONAL aerodynamics , *AIRPLANE design , *MATHEMATICAL models , *ALGORITHMS , *HIGH performance computing - Abstract
Computational aerodynamics is a key technology in aircraft design which is ahead of physical experiment and complements it. Of course all three components of computational modeling are actively developed: mathematical models of real aerodynamic processes, numerical algorithms, and high-performance computing. The most impressive progress has been made in the field of computing, though with a considerable complication of computer architecture. Numerical algorithms are developed more conservative. More precisely, they are offered and theoretically justified for more simple mathematical problems. Nevertheless, computational mathematics now has amassed a whole palette of numerical algorithms that can provide acceptable accuracy and interface between modern mathematical models in aerodynamics and high-performance computers. A significant step in this direction was the European Project ADIGMA whose positive experience will be used in International Project TRISTAM for further movement in the field of computational technologies for aerodynamics. This paper gives a general overview of objectives and approaches intended to use and a description of the recommended four-stage computer technology. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
6. Kinematic calibration of a 2-DOF spatial parallel mechanism.
- Author
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Majarena, A. C., Santolaria, J., Samper, D., and Aguilar, J. J.
- Subjects
- *
KINEMATICS , *DEGREES of freedom , *CALIBRATION , *MATHEMATICAL models , *DATA analysis , *ALGORITHMS , *NUMERICAL analysis - Abstract
This paper presents a new calibration procedure to identify the geometric parameters which improve the kinematic model accuracy of a mechanism. This procedure has been applied to a 2-DOF spatial parallel mechanism, obtaining the identified parameters by means of the direct kinematic model and reducing the position error of the moving platform. Data acquisition is performed by measuring three standard spheres, fixed to the moving platform, by means of a coordinate measuring machine. The method implemented defines an objective function which is optimized though a numerical method based on the Levenberg-Marquardt algorithm. This function compares the measured and calculated moving platform coordinates and minimizes this difference. Results show that in both cases, identification and test position, the position error is reduced considerably. The method developed can be easily generalized to other parallel mechanism. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
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