SP
S.G. Psathas
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This thesis presents a novel framework for solving the Multi-Skill Resource-Constrained Multi-Modal Project Scheduling Problem with maximum time lags, addressing the challenges of scalability, deadline adherence, and uncertainty in job durations. The research is conducted through a case study with the maintenance department of a large European airline, using real-life maintenance scheduling data. To improve scalability, the framework integrates batching techniques that segment the scheduling horizon and a priority-rule-based heuristic to hot start the solver, significantly reducing computational runtimes for large problem instances. A range of objective functions, including single and multi-objective formulations, are explored to evaluate their impact on scheduling performance. The results demonstrate
that multi-objective formulations provide the best balance between throughput and deadline adherence and consistently outperform a priority-based heuristic. A clear trade-off is observed between optimizing for maximum tardiness and average tardiness, where minimizing maximum tardiness improves deadline adherence at the cost of lower throughput, while minimizing average tardiness has a more consistent throughput but allows slightly more deadline misses. To address job duration uncertainty, adaptive buffering strategies based on historical job performance are introduced and shown to outperform static buffers by tailoring slack times to individual job characteristics. In the examined case study, the combination of an adaptive buffering strategy with a multi-objective function combining makespan and
average weighted tardiness offers the most effective trade-off between robustness and efficiency. Overall, the framework proves to be scalable, adaptable, and well-suited to real-world scheduling environments with high variability and complex constraints.
...
that multi-objective formulations provide the best balance between throughput and deadline adherence and consistently outperform a priority-based heuristic. A clear trade-off is observed between optimizing for maximum tardiness and average tardiness, where minimizing maximum tardiness improves deadline adherence at the cost of lower throughput, while minimizing average tardiness has a more consistent throughput but allows slightly more deadline misses. To address job duration uncertainty, adaptive buffering strategies based on historical job performance are introduced and shown to outperform static buffers by tailoring slack times to individual job characteristics. In the examined case study, the combination of an adaptive buffering strategy with a multi-objective function combining makespan and
average weighted tardiness offers the most effective trade-off between robustness and efficiency. Overall, the framework proves to be scalable, adaptable, and well-suited to real-world scheduling environments with high variability and complex constraints.
...
This thesis presents a novel framework for solving the Multi-Skill Resource-Constrained Multi-Modal Project Scheduling Problem with maximum time lags, addressing the challenges of scalability, deadline adherence, and uncertainty in job durations. The research is conducted through a case study with the maintenance department of a large European airline, using real-life maintenance scheduling data. To improve scalability, the framework integrates batching techniques that segment the scheduling horizon and a priority-rule-based heuristic to hot start the solver, significantly reducing computational runtimes for large problem instances. A range of objective functions, including single and multi-objective formulations, are explored to evaluate their impact on scheduling performance. The results demonstrate
that multi-objective formulations provide the best balance between throughput and deadline adherence and consistently outperform a priority-based heuristic. A clear trade-off is observed between optimizing for maximum tardiness and average tardiness, where minimizing maximum tardiness improves deadline adherence at the cost of lower throughput, while minimizing average tardiness has a more consistent throughput but allows slightly more deadline misses. To address job duration uncertainty, adaptive buffering strategies based on historical job performance are introduced and shown to outperform static buffers by tailoring slack times to individual job characteristics. In the examined case study, the combination of an adaptive buffering strategy with a multi-objective function combining makespan and
average weighted tardiness offers the most effective trade-off between robustness and efficiency. Overall, the framework proves to be scalable, adaptable, and well-suited to real-world scheduling environments with high variability and complex constraints.
that multi-objective formulations provide the best balance between throughput and deadline adherence and consistently outperform a priority-based heuristic. A clear trade-off is observed between optimizing for maximum tardiness and average tardiness, where minimizing maximum tardiness improves deadline adherence at the cost of lower throughput, while minimizing average tardiness has a more consistent throughput but allows slightly more deadline misses. To address job duration uncertainty, adaptive buffering strategies based on historical job performance are introduced and shown to outperform static buffers by tailoring slack times to individual job characteristics. In the examined case study, the combination of an adaptive buffering strategy with a multi-objective function combining makespan and
average weighted tardiness offers the most effective trade-off between robustness and efficiency. Overall, the framework proves to be scalable, adaptable, and well-suited to real-world scheduling environments with high variability and complex constraints.
A machine learning classifier can be tricked us- ing adversarial attacks, attacks that alter images slightly to make the target model misclassify the image. To create adversarial attacks on black-box classifiers, a substitute model can be created us- ing model stealing. The research question this re- port address is the topic of using model stealing while minimizing the amount of querying the sub- stitute model needs to train. The solution used in this report is a variant of the ActiveThief algo- rithm that makes use of active learning to deter- mine which data is being queried. The paper exper- iments with different subset selection strategies to find the most informative data points. Also, a seed- ing algorithm based on clustering is explored and finally, a stopping criterion for the ActiveThief al- gorithm is proposed. These variations are evaluated on their accuracy and the number of queries they take to achieve that accuracy. This paper shows cluster seeding is an alternative to random seeding in ActiveThief. This paper also presents different subset selection strategies that outperform the ran- dom sampling strategy. Finally, a stopping criterion based on entropy is introduced that halts the algo- rithm when an uncertainty threshold is reached.
...
A machine learning classifier can be tricked us- ing adversarial attacks, attacks that alter images slightly to make the target model misclassify the image. To create adversarial attacks on black-box classifiers, a substitute model can be created us- ing model stealing. The research question this re- port address is the topic of using model stealing while minimizing the amount of querying the sub- stitute model needs to train. The solution used in this report is a variant of the ActiveThief algo- rithm that makes use of active learning to deter- mine which data is being queried. The paper exper- iments with different subset selection strategies to find the most informative data points. Also, a seed- ing algorithm based on clustering is explored and finally, a stopping criterion for the ActiveThief al- gorithm is proposed. These variations are evaluated on their accuracy and the number of queries they take to achieve that accuracy. This paper shows cluster seeding is an alternative to random seeding in ActiveThief. This paper also presents different subset selection strategies that outperform the ran- dom sampling strategy. Finally, a stopping criterion based on entropy is introduced that halts the algo- rithm when an uncertainty threshold is reached.