“…Many of these are listed and described in Reference 7, including the Voronoi cell method, 67,68 the spectral method, 69 the network approximation method, 70 methods based on FFT, 71 the mesh-free reproducing kernel particle method, 72 finite-volume direct-averaging micromechanics, 73 uniform and nonuniform transformation field analysis, 16,17,[74][75][76] methods of cells, 77 control theory-based methods such as balanced truncation, 78,79 optimal Hankel norm approximation, 80 proper orthogonal decomposition (POD), [81][82][83] data-driven reduced-order methods, [84][85][86][87] ROH, 18,19 and recently data-physics-driven ROH. 52 The FFT, in combination with the Lippmann-Schwinger reformulation of the unit cell problem using an equivalent volume integral equation, greatly speeds up the unit cell computation with little loss of accuracy; thus, this approach has particularly exciting potential. 71,88 However, there are a limited number of examples of its use in practice so far.…”