*2.2. Structure Cross-Sectional Area Discretization*

Primarily, theinvestigated cross-sectional area of the structure, as presentedin Figure 1, was discretized by using two-dimensional discretization mesh characterized by the following formulas [34]:

$$\mathbf{q}\_k(t) = \mathbf{q}(\mathbf{x}, y, t), \qquad \mathbf{x} = \mathbf{i} \cdot \Delta \mathbf{x}, \ y = j \cdot \Delta y \tag{10}$$

$$T\_k(t) = T(\mathbf{x}, y, t), \quad \mathbf{x} = \mathbf{i} \cdot \Delta \mathbf{x}, \ y = j \cdot \Delta y \tag{11}$$

$$j \in \{1, 2, \ldots, n\_x\}, j \in \{1, 2, \ldots, n\_y\}, k \in \{1, 2, \ldots, n\_x \cdot n\_y\}$$

where *nx* and *ny* describe a number of discretization nodes in the *x*-axis and *y*-axis, respectively. On the other hand, the product *nx*·*ny* reflects the entire number of nodes used to discretize the structure's cross-section.

**Figure 1.** Geometry of cross-sectional area of the investigated test structure.

Nodes are numbered from the left to the right side, along the *x*-axis. After reaching the last point in a single row, the next part of the structure, being the nearest row from the top of the current row, was taken into consideration and numbered in the same way. Thus, node no. 1 was placed in the left bottom corner of the structure, while the node with the highest possible number, equal to *nx*·*ny*, was located in the top right corner. The graphical representation of used discretization mesh for analyzed cross-section of the test structure, as well as the way mesh nodes were numbered, is demonstrated in Figure 2. It is also worth highlighted that the distance between nodes in both dimensions was set to 10 nm.

**Figure 2.** The graphical representation of discretization mesh and nodes' numbering. Reprint with permission [34,39]; Copyright 2018, ŁTN.
