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Due to the excellent electromagnetic properties of superconductor materials, superconducting generators have higher efficiency, lower weight and volume than traditional rotating machines. However, it is difficult to simulate the electromagnetic behavior in the superconducting generator due to the nonlinear E–J relationship. A numerical model based on the T–A formulation and moving mesh method is adopted to simulate the superconducting rotating machine, and the electromagnetic and mechanical behaviors of the superconducting rotating machine are investigated. The fully superconducting generator investigated in this article is radial type, which consists of field windings and armature windings made from YBa2Cu3O7−Δ (YBCO) superconducting race-track coils. The anisotropic field-dependent critical current density and the E–J power law relationship are considered in our model. The “virtual tape” model is introduced to calculate the induced current in the T–A formulation. The numerical results are obtained by the finite element method. The electromagnetic results calculated by our model are compared with results from the H–A formulation. The ac losses and stress distributions in superconducting coils are presented based on the T–A formulation. The results show that the body force and stress are periodic, and the stress will concentrate on the boundary of the coil. The magnetic field in the rotor is larger than that in the stator, and the field windings suffer greater body force and stress than the armature windings. This model has acceptable relative error with the H–A model for the time saved following T–A approach and relevance to mechanical calculations. Thus, this model can aid the design of superconducting rotating machines. [ABSTRACT FROM AUTHOR]

Low-temperature Cu–Cu bonding utilizing pillar and concave on silicon substrate with and without polymer layer is successfully implemented at 200 °C under atmospheric pressure. Finite-element method (FEM) simulations on stress and deformation generated during bonding process are also presented in order to discuss their influence on bonding result of several pillar diameters and of concave sidewall angles originating from the manufacturing process. The alteration of parameters in FEM simulations would also be investigated to enhance the bonding outcome. The parameters include the diameter of pillar, the sidewall angle of concave, the shape of the concave opening, the addition of extra polymer layer under Cu concave layer, the bonding temperature, and the pitch of the pillar–concave structure. The implementation of Cu–Cu bonding using pillar–concave structure could have a prospective effect on existing packaging methods in semiconductor industry with benefits of applicability to various sorts of substrates and low bonding temperature. [ABSTRACT FROM PUBLISHER]

In this paper, the relationship between the magnetic properties and microstructures of nanocomposite isotropic exchange-coupled systems with the structure of \alpha -Fe crystalline grains embedded in Nd2Fe14B matrices has been estimated by micromagnetic finite-element method. And then, the results have been analyzed by means of the effectiveness of exchange coupling between the magnetically hard Nd2Fe14B and soft \alpha -Fe phase of the exchange-coupled Nd2Fe 14\text{B}/\alpha -Fe magnetic systems. The effectiveness of interphase exchange coupling has been estimated by the volume fractions of exchange coupling area near phase boundaries between \alpha -Fe grains and Nd2Fe14B matrix. The results have shown the micromagnetic mechanism of the advanced magnetic properties of the exchange coupled magnetic systems with the structure of $\alpha $ -Fe grains embedded in Nd2Fe14B matrix. In addition, the optimal magnetic properties can be expected in the case of comparatively the large grain sizes of $\alpha $ -Fe and Nd2Fe14B phase due to the characteristic structure of those magnetic systems. [ABSTRACT FROM AUTHOR]