@phdthesis{Osagie2023, author = {Osagie, Christian}, title = {Reliability assessment of onshore pipelines based on Bayesian inference}, doi = {10.26127/BTUOpen-6733}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-67338}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {Reliability assessment of pipeline failure factors has become a major concern for industrial firms involved in the transmission of oil and gas, where the requirement to limit these failure factors and their consequences, such as maintenance costs, is particularly significant. Pipelines were constructed throughout time to include safety precautions in order to offer a theoretical minimal failure rate for the pipeline's whole life. This strategy also includes the management of various failure causes as well as routine-based maintenance to assure the dependability of pipelines during their service life. However, the requirement to reduce the impact of these failure factors on pipelines has bolstered the use of reliability evaluation of failure factors on petroleum pipelines. The purpose of this study is to evaluate the reliability of oil pipelines in Nigeria, with emphasis on proposing operational and technical changes to enhance their resilience against unexpected failures. The thesis uses the regular Poisson, empirical, and compound Poisson processes to describe the number of common failure causes owing to corrosion, third-party damage, mechanically induced failure, operational mistakes, and natural hazards in repairable systems. The statistical analysis results serve as the foundation for time to failure modeling of petroleum pipelines utilizing Bayesian inference of the three-parameter Exponentiated Weibull distribution. The thesis also includes reliability probabilistic methods for assessing the influence of uncertainties in pipelines by comparing the First order reliability method (FORM) with the Second order reliability method (SORM) with demonstration on five distinct petroleum pipelines. The probability of failure and the reliability index for the five pipelines were calculated, along with the target reliability. Additionally, the influence of specific pipeline design parameters on the probability of failure was analyzed through sensitivity analysis. This analysis helps identify which design factors have the most significant impact on the likelihood of pipeline failure, allowing for more informed decisions in pipeline design and maintenance practices. By understanding these influences, it is possible to enhance the overall reliability and safety of the pipeline infrastructure. The framework developed in this thesis can be applied to enhance the performance of existing pipelines and serve as a good foundation for the design and implementation of new pipelines and similar infrastructures.}, subject = {Uncertainty; Wahrscheinlichkeit; Oil and gas pipelines; Failures; Analysis; Probability; {\"O}l- und Gaspipelines; Ausf{\"a}lle; Analyse; Unsicherheit; Pipeline; Bayes-Verfahren; Zuverl{\"a}ssigkeit}, language = {en} } @phdthesis{Stolz2023, author = {Stolz, Michael}, title = {Ermittlung und Beurteilung der Zuverl{\"a}ssigkeit von lateralen elektrostatischen Nanoaktoren und ihr Einfluss auf zuk{\"u}nftige Anwendungen}, doi = {10.26127/BTUOpen-6533}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-65332}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {In dieser Dissertation wurden Zuverl{\"a}ssigkeitsaspekte der NED-Aktoren betrachtet und ihre Langzeitstabilit{\"a}t untersucht. Die Langzeituntersuchungen an einzelnen NED-Aktoren haben gezeigt, dass insbesondere große elektrische Felder zur Verk{\"u}rzung der Lebensdauer der Aktorik f{\"u}hren k{\"o}nnen. Elektrische Felder beschleunigen Oxidation der NED-Siliziumelektroden. Dabei wurden zwei unterschiedliche Oxidationsmechanismen beobachtet: die anodische Oxidation von Siliziumelektroden im Isolatorbereich und die feldemissionsunterst{\"u}tzte Oxidation. Die beiden Degradationsmechanismen beg{\"u}nstigen das Wachstum des Siliziumoxides an Siliziumelektroden und resultieren in der Ver{\"a}nderung der Oszillationseigenschaften der NED-Aktoren mit der Zeit. Weitere Untersuchungen an den NED-basierten Anwendungen - Mikrolautsprecher haben verdeutlicht, dass solche Faktoren wie Feuchtigkeit die Degradation am meisten forcieren. Durch Passivierung der Aktoren, wobei sie z. B. mit Aluminiumoxid im ALD-Verfahren verkapselt werden, k{\"o}nnen unerw{\"u}nschte Degradationsmechanismen deutlich verlangsamt werden. Durch eine geeignete Materialwahl bei der Verkapselung kann sogar gleichzeitig die Effizienz der Aktoren verbessert werden.}, subject = {Nanoaktor; NED; Zuverl{\"a}ssigkeit; MEMS; Nanoscopic electrostatic drive; Nano actuators; Reliability; Mikroaktor; MEMS; Zuverl{\"a}ssigkeit}, language = {de} }