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Abstract: We revisit in this paper the theory of axisymmetric vortex rings in an ideal fluid. The boundary separating the vortex ring from the external (potential) flow is assumed of elliptic shape. For a given distribution of vorticity in the vortex core, we theoretically put into evidence the critical parameter for the existence of non-trivial solutions, thus confirming the numerical observation of Durst et al. [ZAMP 32 (1981) 156]. A sharp estimation of the critical threshold is analytically derived. Theoretical predictions are confirmed by numerical simulations using finite elements. A new numerical algorithm is presented and shown to display better performances compared to previous published algorithms using finite differences. The convergence of the iterative algorithm is proved using the theory of elliptic partial differential equations with discontinuous nonlinearities. [Copyright &y& Elsevier]

Abstract: With the rapid increase in circuit complexity, accurate reliability simulator is necessary as reliability testing for fabricated circuit is progressively more time and resource consuming. Simple 2D electromigration (EM) simulator has many limitations and most of the 3D EM simulations in the literature are using simple line-via structure which is only part of the real circuit structure. In this paper, a thorough comparison between simple 3D line-via structure model and 3D circuit model under different test conditions is performed using class-AB amplifier as an example, and the results showed that simple line-via structure simulation may not always correctly represent the real circuit failure site. [Copyright &y& Elsevier]

Abstract: In this paper a detailed mathematical model for an electromagnetic energy harvesting architecture based on a semi-analytical approach is introduced. This model estimates the generated energy of the architecture by computing the static and dynamic magnetic and electric fields that describe its dynamics. A comparison of the static fields with the results of a Finite Element Analysis simulation in COMSOL Multiphysics shows good agreement. The model also features increased accuracy and numerical stability. In the model the semi-analytical solutions for the electromagnetic damping force exerted by the induced current coil and the induced electromotive force on the coil provide additional insight into the interactions of electromagnetic induction and damping. Additionally, the energy estimation could be used as a figure of merit in an maximization process to identify the optimal dimensions of the energy harvester. [Copyright &y& Elsevier]