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Examples of modified re-entrant structures, which can be seen as variations in the units in Figure 1, proposed by (a) Lu et al. (2016) [140]; (b) Bezazi et al. (2005) [135] and Harkati et al. (2017) [128]; (c) Gohar et al. (2021) [127]; (d) Huang et al. (2017) [141]; (e) Khan et al. (2019) [59] and Mustahsan et al. (2022) [142]; (f) Guo et al. (2020) [143]; (g) Wang et al. (2023) [144]; and (h) Zhang et al. (2021) [145] and (i) Li et al. (2022) [129].
