Figure 3
The image contains four panels labelled a to d, each plotting x 1 on the horizontal axis and x 2 on the vertical axis, with values from about negative 6 to positive 6. In all panels, a closed irregular boundary labelled theoretical G of x equals 0 defines a central region. A dashed curve labelled ensemble model approximates this boundary. Circular markers show initial samples distributed across the space. Square markers show selected samples added progressively. Panel a shows one selected sample near the lower left boundary. Panel b shows several selected samples along the upper and right boundary. Panel c adds more selected samples tracing most boundary segments. Panel d shows dense selected samples closely following the entire theoretical boundary.The active learning process of reliability analysis in Example 1
Note(s): (a) 1 selected sample, (b) 4 selected samples, (c) 10 selected samples and (d) 20 selected samples