The Experts below are selected from a list of 70245 Experts worldwide ranked by ideXlab platform
I V Moskalenko - One of the best experts on this subject based on the ideXlab platform.
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Propagation of cosmic ray nucleons in the galaxy
The Astrophysical Journal, 1998Co-Authors: A W Strong, I V MoskalenkoAbstract:We describe a method for the numerical computation of the Propagation of primary and secondary nucleons, primary electrons, and secondary positrons and electrons. Fragmentation and energy losses are computed using realistic distributions for the interstellar gas and radiation fields, and diffusive reacceleration is also incorporated. The models are adjusted to agree with the observed cosmic-ray B/C and 10Be/9Be ratios. Models with diffusion and convection do not account well for the observed energy dependence of B/C, while models with reacceleration reproduce this easily. The height of the halo Propagation region is determined using recent 10Be/9Be measurements as >4 kpc for diffusion/convection models and 4-12 kpc for reacceleration models. For convection models, we set an upper limit on the velocity gradient of dV/dz < 7 km s-1 kpc-1. The radial distribution of cosmic-ray sources required is broader than current estimates of the supernova remnant (SNR) distribution for all halo sizes. Full details of the numerical method used to solve the cosmic-ray Propagation Equation are given.
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Propagation of cosmic ray nucleons in the galaxy
arXiv: Astrophysics, 1998Co-Authors: A W Strong, I V MoskalenkoAbstract:We describe a method for the numerical computation of the Propagation of primary and secondary nucleons, primary electrons, and secondary positrons and electrons. Fragmentation and energy losses are computed using realistic distributions for the interstellar gas and radiation fields, and diffusive reacceleration is also incorporated. The models are adjusted to agree with the observed cosmic-ray B/C and 10Be/9Be ratios. Models with diffusion and convection do not account well for the observed energy dependence of B/C, while models with reacceleration reproduce this easily. The height of the halo Propagation region is determined, using recent 10Be/9Be measurements, as >4 kpc for diffusion/convection models and 4-12 kpc for reacceleration models. For convection models we set an upper limit on the velocity gradient of dV/dz < 7 km/s/kpc. The radial distribution of cosmic-ray sources required is broader than current estimates of the SNR distribution for all halo sizes. Full details of the numerical method used to solve the cosmic-ray Propagation Equation are given.
Ronald G Hadley - One of the best experts on this subject based on the ideXlab platform.
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the complex jacobi iterative method for three dimensional wide angle beam Propagation
Optics Express, 2008Co-Authors: R Godoyrubio, Ronald G HadleyAbstract:A new complex Jacobi iterative technique adapted for the solution of three-dimensional (3D) wide-angle (WA) beam Propagation is presented. The beam Propagation Equation for analysis of optical Propagation in waveguide structures is based on a novel modified Pade(1,1) approximant operator, which gives evanescent waves the desired damping. The resulting approach allows more accurate approximations to the true Helmholtz Equation than the standard Pade approximant operators. Furthermore, a performance comparison of the traditional direct matrix inversion and this new iterative technique for WA-beam Propagation method is reported. It is shown that complex Jacobi iteration is faster and better-suited for large problems or structures than direct matrix inversion.
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a three dimensional non paraxial beam Propagation method using complex jacobi iteration
Lasers and Electro-Optics Society Meeting, 2008Co-Authors: Khai Le Quang, R Godoyrubio, Ronald G HadleyAbstract:A new complex Jacobi iterative technique adapted for the solution of three-dimensional (3D) non-paraxial beam Propagation is presented. The beam Propagation Equation for analysis of optical Propagation in waveguide structures is based on a novel modified Pade(1,1) approximant operator we recently proposed. The effectiveness of our new approach is demonstrated in comparison with the traditional direct matrix inversion. Our method is targeted towards large waveguide structures with a long path length.
Peter Bienstman - One of the best experts on this subject based on the ideXlab platform.
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fast three dimensional generalized rectangular wide angle beam Propagation method using complex jacobi iteration
Journal of The Optical Society of America B-optical Physics, 2009Co-Authors: Peter BienstmanAbstract:A fast and efficient three-dimensional generalized rectangular wide-angle beam Propagation method (GR-WA-BPM) based on a recently proposed modified Pade (1,1) approximant is presented. In our method, at each Propagation step, the beam Propagation Equation is recast in terms of a Helmholtz Equation with a source term, which is solved quickly and accurately by a recently introduced complex Jacobi iterative (CJI) method. The efficiency of the GR-WA-BPM for the analysis of tilted optical waveguides is demonstrated in comparison with the standard wide-angle beam Propagation method based on Hadley's scheme. In addition, since the utility of the CJI method depends mostly on its execution speed in comparison with the traditional direct matrix inversion, several performance comparisons are also presented.
H. Kawaguchi - One of the best experts on this subject based on the ideXlab platform.
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Analysis of basic four-wave mixing characteristics in a semiconductor optical amplifier by the finite-difference beam Propagation method
IEEE Journal of Quantum Electronics, 2000Co-Authors: Y. Yamayoshi, H. KawaguchiAbstract:We have numerically analyzed nondegenerate four-wave mixing (FWM) among short optical pulses in a semiconductor optical amplifier (SOA) by the finite-difference beam Propagation method (FD-BPM). We used the nonlinear Propagation Equation taking into account gain spectrum dynamic gain saturation which depends on carrier depression, carrier heating, and spectral hole-burning, group velocity dispersion, self-phase modulation, and two-photon absorption. To analyze FWM in an SOA, the evolution in time and spectral domain of two input optical pulses with different frequencies during Propagation was calculated. From this simulation, it has become clear that the method me used here is a very useful technique for simulating FWM characteristics in SOA's. We also found that the wavelength dependence of the gain is crucial if the detuning is larger than 1 THz.
R Godoyrubio - One of the best experts on this subject based on the ideXlab platform.
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the complex jacobi iterative method for three dimensional wide angle beam Propagation
Optics Express, 2008Co-Authors: R Godoyrubio, Ronald G HadleyAbstract:A new complex Jacobi iterative technique adapted for the solution of three-dimensional (3D) wide-angle (WA) beam Propagation is presented. The beam Propagation Equation for analysis of optical Propagation in waveguide structures is based on a novel modified Pade(1,1) approximant operator, which gives evanescent waves the desired damping. The resulting approach allows more accurate approximations to the true Helmholtz Equation than the standard Pade approximant operators. Furthermore, a performance comparison of the traditional direct matrix inversion and this new iterative technique for WA-beam Propagation method is reported. It is shown that complex Jacobi iteration is faster and better-suited for large problems or structures than direct matrix inversion.
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a three dimensional non paraxial beam Propagation method using complex jacobi iteration
Lasers and Electro-Optics Society Meeting, 2008Co-Authors: Khai Le Quang, R Godoyrubio, Ronald G HadleyAbstract:A new complex Jacobi iterative technique adapted for the solution of three-dimensional (3D) non-paraxial beam Propagation is presented. The beam Propagation Equation for analysis of optical Propagation in waveguide structures is based on a novel modified Pade(1,1) approximant operator we recently proposed. The effectiveness of our new approach is demonstrated in comparison with the traditional direct matrix inversion. Our method is targeted towards large waveguide structures with a long path length.
