# Project Robust Scheduling Based on the Scattered Buffer Technology
## 5 Experimental Analysis
### Analysis of Experimental Results
#### 5.2.2 Impact of Activity Duration Randomness on the Robust Schedule  
When \(Duet=1.10\times C_{min}\), three groups of problems (\(J10\), \(J20\) and \(J30\)) were tested and solved, respectively. Table 2 shows simulation results of \(J10\), \(J20\) and \(J30\) under different activity variance (\(\sigma\)). (1) With the enhancement of the activity duration variability:  
1 In terms of the solution robustness, the value of \(SP\) in UAS is the same as in RFDFF and STC, although it has a slight decline. With the enhancement of the activity duration variability, the trend remains unchanged later. This indicates that UAS is highly adaptive to the uncertainty of the activity duration, and it can guarantee the stability of start time of most activities. Conversely, the value of \(SC\) presents a trend of gradually increasing. This is because the value of \(SP\) refers to the relative index of the activity quantity, while the value of \(SC\) is the absolute index of the time delay. The increase of the value of \(SC\) only indicates that the realized start time of the delayed activity increases compared with \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Problem**} & \multirow{2}{*}{**Robustness Metrics**} & \multicolumn{3}{c}{\(\sigma=0.3\)} & \multicolumn{3}{c}{\(\sigma=0.6\)} & \multicolumn{3}{c}{\(\sigma=0.9\)} \\ \cline{3-11}  & & **RFDFF** & STC & **UAS** & **RFDFF** & **STC** & **UAS** & **RFDFF** & **STC** & **UAS** \\ \hline \multirow{4}{*}{\(J10\)} & SP & 0.8117 & 0.8165 & 0.8401 & 0.7640 & 0.7590 & 0.7776 & 0.7657 & 0.7585 & 0.7733 \\  & SC & 19.5327 & 18.6960 & 14.0884 & 48.2386 & 52.3135 & 43.8052 & 83.7207 & 88.8957 & 79.7710 \\  & TPCP & 0.7417 & 0.7454 & 0.7416 & 0.6152 & 0.6154 & 0.6162 & 0.9977 & 0.9963 & 0.5980 \\  & APL & 33.1488 & 33.1196 & 33.1661 & 34.6062 & 34.6046 & 34.5928 & 36.2456 & 36.2775 & 36.2419 \\ \hline \multirow{4}{*}{\(J20\)} & SP & 0.7520 & 0.7654 & 0.7709 & 0.6967 & 0.6989 & 0.7016 & 0.7010 & 0.7018 & 0.7041 \\  & SC & 78.674 & 27.5052 & 64.5783 & 191.2419 & 196.3070 & 18.9613 & 336.7798 & 34.2054 & 30.9924 \\  & TPCP & 0.6698 & 0.6776 & 0.6678 & 0.5175 & 0.5158 & 0.5134 & 0.4826 & 0.4850 & 0.4828 \\ \hline \multirow{4}{*}{\(J30\)} & APL & 54.5441 & 54.3327 & 54.4847 & 57.7925 & 57.6623 & 57.7660 & 61.7850 & 61.7099 & 61.8216 \\  & SP & 0.7416 & 0.7752 & 0.7465 & 0.6970 & 0.7081 & 0.6938 & 0.7019 & 0.7063 & 0.6924 \\  & SC & 145.3222 & 114.7046 & 115.1642 & 249.4382 & 240.4390 & 233.2613 & 392.4993 & 397.3236 & 400.9541 \\  & TPCP & 0.6064 & 0.6151 & 0.6201 & 0.4543 & 0.6163 & 0.4607 & 0.4210 & 0.4232 & 0.4190 \\  & APL & 69.9003 & 69.9853 & 69.9993 & 74.0973 & 74.2202 & 73.9554 & 79.7130 & 79.7725 & 79.9574 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The impact of stochastic activity duration on the robustness when \(Duet=1.10\times C_{\min}\). the predicted one and the value of \(SC\) increases gradually. The experimental results on the value of \(SP\) and \(SC\) show that UAS has better solution robustness. 2 In terms of quality robustness, UAS is the same as RFDFF and STC: the timely project completion probability (\(TPCP\)) of the project will gradually decrease, and the value of average project length (\(APL\)) of project will gradually increase. This is because UAS is mainly used to protect the stability of start time of activity, but it is difficult to ensure that the project will be complicated on schedule during the period when the activity duration variability increases. With the increase of activity uncertainty, the possibility that the project is delayed to be completed will increase; the average project length will gradually increase. (2) With the increment of the project scale:  
1 In terms of solution robustness, when the uncertainty of activity duration is relatively smaller, UAS is the same as RFDFF and STC: the solution robustness will gradually decrease, namely the value of \(SP\) will gradually decrease, and the value of \(SC\) will gradually increase.