Finite element analysis of multi-stage deep drawing for forming deep rectangular case with high aspect ratio

This paper presents investigations on multi-stage deep drawing for producing a flat and deep rectangular case, of which a cross section is high aspect ratio. Effects of a blank shape on a formability was investigated for preventing a local thinning and a large ear by using the finite element method (FEM) analysis. The multi-stage deep drawing was composed of four stages. The first and the second stage were deep drawing and redrawing process, and the third and the fourth stage were ironing process. The blank was the rectangle with the elliptic corners, and the longitudinal length and the elliptic corner length was changed. The local thinning and the ear were reduced by appropriately setting the longitudinal length and the elliptic corner length. In addition, the effect of the aspect ratio on the formability was small. Therefore, the optimized blank could be applied for forming the flat and deep rectangular case with various aspect ratio

Exact results for nonlinear Drude weights in the spin- 12 XXZ chain

Nonlinear Drude weight (NLDW) is a generalization of the linear Drude weight, which characterizes the nonlinear transport in quantum many-body systems. We investigate these weights for the spin-12 XXZ chain in the critical regime. The effects of the Dzyaloshinskii-Moriya interaction and an external magnetic field are also studied. Solving the Bethe equations numerically, we obtain these weights for very large system sizes and identify parameter regimes where the weights diverge in the thermodynamic limit. These divergences appear in all the orders studied in this Letter and can be regarded as a generic feature of the NLDWs. We study the origin of these divergences and reveal that they result from nonanalytic finite-size corrections to the ground-state energy. Furthermore, we compute closed-form expressions for several weights in the thermodynamic limit and find excellent agreement with the numerical results

Topological d-wave superconductivity in two dimensions

Despite intensive searches for topological superconductors, the realization of topological superconductivity remains under debate. Previous proposals for the topological s-wave, p-wave, and chiral d-wave superconductivity have both advantages and disadvantages. In this review, we discuss two-dimensional topological superconductivity based on the non-chiral d-wave superconductors. It is shown that the noncentrosymmetric d-wave superconductors become topological superconductors under an infinitesimal Zeeman field without fine-tuning of parameters. Floquet engineering for introducing the Zeeman field in a controllable way is also proposed. When the two-dimensional noncentrosymmetric superconductors are stacked to recover the global inversion symmetry, the field-induced parity transition may occur, and the high-field odd-parity superconducting state realizes various topological phases depending on the stacking structures. Two-dimensional heterostructures of strongly correlated electron systems, which have been developed by recent experiments, are proposed as a platform of the high-temperature topological superconductivity and the interplay of topology and strong correlations in superconductors