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Table 6 Notation of the ordering algorithm
Notation | Description |
|---|---|
\(i\) | Asset index |
\(n\) | Total number of considered assets |
\(r\) | Run index |
\(k\) | Index of the iteration for each run \(r\) |
\({t}_{i}^{k,r}\) | Time of execution of the maintenance of asset \(i\) in the sequence defined at iteration \(k\) of run \(r\) |
\(\widetilde{k}\) | Number of iterations after which the parameter \(b\) changes its value |
\(K\) | Maximum number of the considered iterations for each run \(r\) |
\(R\) | Total number of runs |
\({DD}_{i}^{\tau }\) | Due date of the maintenance intervention according to asset status |
\({\pi }_{i}\) | Static asset criticality related to the type of asset |
\({\pi p}_{i}^{\tau }\) | Asset criticality in the considered time horizon τ related to the passenger flow |
\(p\left(k,r,i\right)\) | Position of asset \(i\) in the sequence at iteration \(k\) of run \(r\) |
\({e}_{i}\) | Time penalty for postponing asset \(i\) in the sequence, that is, the average duration of maintenance execution |
\({S}_{{j}_{\left(k-1\right),r}i}\) | Distance between the asset and the previous one at the iteration \(k-1\) of run \(r\) |
\({S}_{{ih}_{\left(k-1\right),r}}\) | Distance between the asset and the following one at the iteration \(k-1\) of run \(r\) |
\({\alpha }_{l}\) | Weights to be calibrated |
\({t}_{i}^{k,r}-{DD}_{i}\) | Indication of asset degradation/status |