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Program 2022 Spring
| When | Who | What |
|---|---|---|
| 07.04.2022 | Ph.D. Candidate Emefon Dan | More information will come later. |
| 24.03.2022 | Ph.D. Candidate Bahareh Tajiani | Title: Lead Time Modeling for Optimization of an Alarm Threshold DescriptionAbstract: Lead time is the time from when a spare part is ordered until it arrives, or it is the time from when a maintenance action is ordered until it is carried out. Most recent literatures focused on deterministic lead time in maintenance context to find an optimal maintenance policy, however in real-life applications, lead time is a stochastic variable depending on many factors such as availability of the maintenance team, type of failure, delivery time of an item, etc. In this presentation, we will discuss the deterministic and stochastic lead time modeling for the continuously monitored systems subject to gradual degradation in order to find an optimal alarm threshold. Furthermore, some ideas will be proposed regarding how the model can be improved to consider different failure mechanisms such as external shocks. About Speaker:Bahareh Tajiani has a BSc in Industrial Engineering from Iran and a MSc in RAMS from NTNU. She started her work as a PhD candidate at RAMS group, MTP, NTNU in August 2019. Her PhD working title is mathematical modeling for remaining useful life (RUL) prediction of bearings which is an internal project at NTNU. |
| 10.03.2022 | Ph.D. Candidate Jie Liu | Title: A comparison study for bearing remaining useful life prediction by using standard stochastic approach and digital twin Abstract: The topic of the presentation is about comparison of RUL prediction models which including stochastic approaches and digital twin of Matlab. Data used for prediction is from experiment of RAMS lab. Two stochastic approaches are selected which are Wiener process and Geometric Brownian Motion. The purpose of the study is to compare the models for remaining useful life prediction with standard stochastic approaches and digital twin through real degradation data and try to find the comparison among them. The research could be used as a reference for further remaining useful life prediction research. About Speaker: Jie Liu has a bachelor’s degree in Applied Mathematics in Beijing Institute of Technology from China and a master’s degree in RAMS of NTNU. She started as a PhD candidate at RAMS group, MTP, NTNU in September 2021. Her research topic is Digital Twin Qualification for Maintenance, which is a part of SUBPRO project. |
24.02.2022 15:00 - 18:00 | Ph.D. Candidate Nanda Anugrah Zikrullah | There will be no seminar this week. Instead, you are invited to Nanda Anugrah Zikrullah’s defense.
More information can be found here. |
09.02.2022 10:30-11:30 | Guest Ph.D Candidate Danilo Colombo | Title: Optimizing the testing policy for the Blowout Preventer Abstract: The topic of the presentation is the optimization of the testing policy of a subsea Blowout Preventer (BOP). The subsea BOP is a safety-critical equipment used during the construction or intervention in a well. It is installed at the top of the wellhead, near the seabed, and connects the well with the rig via riser. When a kick occurs, i. e., the formation fluids start to flow into the wellbore, the BOP is activated and acts like a valve, sealing the well and preventing an oil spill from occurring. To ensure its availability and safety, the BOP is periodically tested, which entails the operation to be stopped. The tests are done usually according to the best practices (e.g. regulations, standards). The downtime due to the testing period may have a significant economic impact. The aim of this study is to optimize the test strategy for BOP reducing costs while satisfying the integrity lever required. To do so it will be considered three kinds of tests: (i) functional tests, (ii) partial pressure tests; and (iii) maximum pressure tests. The study will investigate a formulation for the test coverage and costs of each test. The test policy should consider the last overhaul of the BOP (i.e., the age of components) and failures that lead to a loss of redundancy in the system, which affects the probability of having a safety impact. Possible future developments are: (i) to include the degradation caused by the test; (ii) to consider dependent failures. About Speaker: Guest Ph.D Candidate from Brazil, Danilo Colombo. He is a mechatronics engineer and obtained a M.Sc in Production Engineer with the work in Markov chains to model the subsea well integrity. He is a petroleum engineer at Petrobras and he is currently an advisor in reliability and risk analysis at the CENPES Research Center. He is a member of SPE (Society of Petroleum Engineers) and ABRISCO (Brazilian Association of Risk, Reliability and System Safety). |
| 27.01.2022 | Ph.D. Candidate Lin Xie | There will be no seminar this week. Instead, you are invited to Lin Xie’s defense.
Check the program for more information. Lin Xie_english program.pdf |
13.01.2022 (Digital only) | Ph.D. Candidate Lin Xie | Title: Safety barriers in complex systems with dependent failures—Modeling and assessment approaches Abstract: Technical systems are becoming more and more complex with a degree of dependencies. Such dependency issues can significantly reduce system reliability and cause catastrophes without proper prevention. Therefore, a variety of control measures, such as safety barriers, are necessary to be adopted against dependent failures and ensure the safety of technical systems. However, in the current literature, neither the effects of dependent failures within safety barriers nor the impact of safety barriers against dependent failures has been well studied. Therefore, it is desirable to analyze and model the effects of safety barriers in complex systems considering dependency issues, such as dependency between safety barriers and the environment, dependent failures within safety barriers, and safety barriers against dependent failures. The Ph.D. thesis bridges safety barriers and complex systems by considering the dependency issues. The aim is broken into four objectives addressed in five journal articles and three conference articles. |
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