المؤلفون: Zhong Wan-xie, Zheng Chang-liang, Chen Jie-Fu

المصدر: Acta Physica Sinica. 55:2340

مصطلحات موضوعية: Symplectic vector space, Mathematical analysis, General Physics and Astronomy, Computational electromagnetics, Symplectic integrator, Eigenfunction, Mathematics::Symplectic Geometry, Finite element method, Mathematics, Symplectic manifold, Hamiltonian system, Symplectic geometry

الوصف: The governing equations for the electromagnetic waveguide are derived to Hamiltonian system formulation and symplectic geometric form, and transverse electric and magnetic components are treated as dual vectors to each other. By separation of variables, we arrived at a symplectic eigenvalue problem for Hamiltonian operator matrix, which can be solved by adjoint symplectic orthonormal relationship and the symplectic eigenfunction expansion method. A dual edge element is proposed for electromagnetic waveguide with irregular cross section and inhomogeneous loaded materials. Dual edge element can surmount those difficulties related to node-based finite elements in computational electromagnetics, and our numerical examples show that dual edge element has its own merits when compared with regular edge element.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::031f0783b36c40c14203e8bd3b2a13c5Test
https://doi.org/10.7498/aps.55.2340Test

المؤلفون: Zhong Wan-xie, Chen Jie-Fu, Liu Wan-Qiu

المصدر: Acta Physica Sinica. 55:884

مصطلحات موضوعية: Optimal design, Quality (physics), Frequency selectivity, Bloch equations, Global optimization algorithm, Electronic engineering, General Physics and Astronomy, Time integral, Radio frequency, Algorithm, Mathematics

الوصف: Solving the Bloch equations is a core procedure in the optimal design of radio frequency pulses, which has direct impacts on the quality of acquired images in magnetic resonance imaging. Although the analytical solutions of the Bloch equations exist under some circumstances, they hardly can be applied for practical use because of their complexity and lack of generality. In this paper, we employ precise time integration to solve the Bloch equations. Based on a high precision algorithm and in conjunction with a global optimization algorithm, we provide a complate procedure for the design of radio frequency pulses. The numerical data listed at the end of this paper demonstrate that the pulses derived from our algorithm have good frequency selectivity.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::b166d352a028e62a0c29c5b2da4f6f93Test
https://doi.org/10.7498/aps.55.884Test