The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform

Alexanda Djordjevich - One of the best experts on this subject based on the ideXlab platform.

Svetislav Savovic - One of the best experts on this subject based on the ideXlab platform.

  • numerical solution of the power Flow Equation in step index plastic optical fibers
    Journal of The Optical Society of America B-optical Physics, 2004
    Co-Authors: Alexanda Djordjevich, Svetislav Savovic
    Abstract:

    The numerical solution of the complete power Flow Equation is reported and employed to investigate the state of mode coupling along a step-index plastic optical fiber. This solution is based on the explicit finite-difference method and, in contrast to earlier solutions, does not neglect absorption and scattering loss. It is the only solution that can accommodate any input condition throughout the entire range of feasible input angles without the need for restriction to those angles that are sufficiently far away from critical. Our results for the field patterns at different locations along one type of fiber are in agreement with reported measurements earlier. Furthermore, the length of fiber required for achieving a steady-state mode distribution matches the analytical solution that is available for such distribution as a special case. Mode coupling in plastic fibers is known to affect fiber-optic power delivery, data transmission, and sensing systems.

  • investigation of mode coupling in step index plastic optical fibers using the power Flow Equation
    IEEE Photonics Technology Letters, 2000
    Co-Authors: Alexanda Djordjevich, Svetislav Savovic
    Abstract:

    Using the power Flow Equation, we have examined the mode coupling caused by intrinsic perturbation effects of the step index plastic optical fiber. A numerical solution has been obtained by the explicit finite difference method. Results show the state of mode coupling along the fiber. They indicate that the equilibrium mode distribution is achieved at much shorter lengths compared to the case with glass fibers.

Michel Mareschal - One of the best experts on this subject based on the ideXlab platform.

  • test of a new heat Flow Equation for dense fluid shock waves
    Journal of Chemical Physics, 2010
    Co-Authors: Brad Lee Holian, Michel Mareschal, Ramon Ravelo
    Abstract:

    Using a recently proposed Equation for the heat-flux vector that goes beyond Fourier’s Law of heat conduction, we model shockwave propagation in the dense Lennard-Jones fluid. Disequilibrium among the three components of temperature, namely, the difference between the kinetic temperature in the direction of a planar shock wave and those in the transverse directions, particularly in the region near the shock front, gives rise to a new transport (equilibration) mechanism not seen in usual one-dimensional heat-Flow situations. The modification of the heat-Flow Equation was tested earlier for the case of strong shock waves in the ideal gas, which had been studied in the past and compared to Navier–Stokes–Fourier solutions. Now, the Lennard-Jones fluid, whose Equation of state and transport properties have been determined from independent calculations, allows us to study the case where potential, as well as kinetic contributions are important. The new heat-Flow treatment improves the agreement with nonequilibr...

  • heat Flow Equation motivated by the ideal gas shock wave
    Physical Review E, 2010
    Co-Authors: Brad Lee Holian, Michel Mareschal
    Abstract:

    We present an Equation for the heat-flux vector that goes beyond Fourier's Law of heat conduction, in order to model shockwave propagation in gases. Our approach is motivated by the observation of a disequilibrium among the three components of temperature, namely, the difference between the temperature component in the direction of a planar shock wave, versus those in the transverse directions. This difference is most prominent near the shock front. We test our heat-Flow Equation for the case of strong shock waves in the ideal gas, which has been studied in the past and compared to Navier-Stokes solutions. The new heat-Flow treatment improves the agreement with nonequilibrium molecular-dynamics simulations of hard spheres under strong shockwave conditions.

Brad Lee Holian - One of the best experts on this subject based on the ideXlab platform.

  • test of a new heat Flow Equation for dense fluid shock waves
    Journal of Chemical Physics, 2010
    Co-Authors: Brad Lee Holian, Michel Mareschal, Ramon Ravelo
    Abstract:

    Using a recently proposed Equation for the heat-flux vector that goes beyond Fourier’s Law of heat conduction, we model shockwave propagation in the dense Lennard-Jones fluid. Disequilibrium among the three components of temperature, namely, the difference between the kinetic temperature in the direction of a planar shock wave and those in the transverse directions, particularly in the region near the shock front, gives rise to a new transport (equilibration) mechanism not seen in usual one-dimensional heat-Flow situations. The modification of the heat-Flow Equation was tested earlier for the case of strong shock waves in the ideal gas, which had been studied in the past and compared to Navier–Stokes–Fourier solutions. Now, the Lennard-Jones fluid, whose Equation of state and transport properties have been determined from independent calculations, allows us to study the case where potential, as well as kinetic contributions are important. The new heat-Flow treatment improves the agreement with nonequilibr...

  • heat Flow Equation motivated by the ideal gas shock wave
    Physical Review E, 2010
    Co-Authors: Brad Lee Holian, Michel Mareschal
    Abstract:

    We present an Equation for the heat-flux vector that goes beyond Fourier's Law of heat conduction, in order to model shockwave propagation in gases. Our approach is motivated by the observation of a disequilibrium among the three components of temperature, namely, the difference between the temperature component in the direction of a planar shock wave, versus those in the transverse directions. This difference is most prominent near the shock front. We test our heat-Flow Equation for the case of strong shock waves in the ideal gas, which has been studied in the past and compared to Navier-Stokes solutions. The new heat-Flow treatment improves the agreement with nonequilibrium molecular-dynamics simulations of hard spheres under strong shockwave conditions.

William W.-g. Yeh - One of the best experts on this subject based on the ideXlab platform.

  • A reduced‐order model for groundwater Flow Equation with random hydraulic conductivity: Application to Monte Carlo methods
    Water Resources Research, 2013
    Co-Authors: Damiano Pasetto, Mario Putti, William W.-g. Yeh
    Abstract:

    [1] We present a model-order reduction technique that overcomes the computational burden associated with the application of Monte Carlo methods to the solution of the groundwater Flow Equation with random hydraulic conductivity. The method is based on the Galerkin projection of the high-dimensional model Equations onto a subspace, approximated by a small number of pseudo-optimally chosen basis functions (principal components). To obtain an efficient reduced-order model, we develop an offline algorithm for the computation of the parameter-independent principal components. Our algorithm combines a greedy algorithm for the snapshot selection in the parameter space and an optimal distribution of the snapshots in time. Moreover, we introduce a residual-based estimation of the error associated with the reduced model. This estimation allows a considerable reduction of the number of full system model solutions required for the computation of principal components. We demonstrate the robustness of our methodology by way of numerical examples, comparing the empirical statistics of the ensemble of the numerical solutions obtained using the traditional Monte Carlo method and our reduced model. The numerical results show that our methodology significantly reduces the computational requirements (CPU time and storage) for the solution of the Monte Carlo simulation, ensuring a good approximation of the mean and variance of the head. The analysis of the empirical probability density functions at the observation wells suggests that our reduced model produces good results and is most accurate in the regions with large drawdown.

  • a reduced order model for groundwater Flow Equation with random hydraulic conductivity application to monte carlo methods
    Water Resources Research, 2013
    Co-Authors: Damiano Pasetto, Mario Putti, William W.-g. Yeh
    Abstract:

    [1] We present a model-order reduction technique that overcomes the computational burden associated with the application of Monte Carlo methods to the solution of the groundwater Flow Equation with random hydraulic conductivity. The method is based on the Galerkin projection of the high-dimensional model Equations onto a subspace, approximated by a small number of pseudo-optimally chosen basis functions (principal components). To obtain an efficient reduced-order model, we develop an offline algorithm for the computation of the parameter-independent principal components. Our algorithm combines a greedy algorithm for the snapshot selection in the parameter space and an optimal distribution of the snapshots in time. Moreover, we introduce a residual-based estimation of the error associated with the reduced model. This estimation allows a considerable reduction of the number of full system model solutions required for the computation of principal components. We demonstrate the robustness of our methodology by way of numerical examples, comparing the empirical statistics of the ensemble of the numerical solutions obtained using the traditional Monte Carlo method and our reduced model. The numerical results show that our methodology significantly reduces the computational requirements (CPU time and storage) for the solution of the Monte Carlo simulation, ensuring a good approximation of the mean and variance of the head. The analysis of the empirical probability density functions at the observation wells suggests that our reduced model produces good results and is most accurate in the regions with large drawdown.