A maintenance model is put forward for equipment, which is subjected to internal and external failures. In the model, two maintenance pollcies--perfect minimal repair and replacement are considered. The operational ti...A maintenance model is put forward for equipment, which is subjected to internal and external failures. In the model, two maintenance pollcies--perfect minimal repair and replacement are considered. The operational time has a phase type distribution （PH distribution）. Failures＇ arrival follows a Markovian Arrival Process （MAP）. Some failures require the replacement of the system, and others minimal repairs. The performance measures-the mean number of minimal repairs and replacements are analyzed and calculated.展开更多
In accordance with the concept of the potential failure of plant, it can be divided into three states: normal, potential failure and functional failure. The intervals of the plant from new to when the potential failur...In accordance with the concept of the potential failure of plant, it can be divided into three states: normal, potential failure and functional failure. The intervals of the plant from new to when the potential failure and from potential failure to functional failure are regarded, in this paper, as a random variables. Numerical examples indicate both the nature and sensitivity of the output from the models.展开更多
Civil aircraft maintenance process simulation model is an effective method for analyzing the maintainability of a civil aircraft. First, we present the Hierarchical Colored Timed Petri Nets for maintenance process mod...Civil aircraft maintenance process simulation model is an effective method for analyzing the maintainability of a civil aircraft. First, we present the Hierarchical Colored Timed Petri Nets for maintenance process modeling of civil aircraft. Then, we expound a general method of civil aircraft maintenance activities, determine the maintenance level for decomposition, and propose the methods of describing logic of relations between the maintenance activities based on Petri Net. Finally, a time Colored Petri multi-level network modeling and simulation procedures and steps are given with the maintenance example of the landing gear burst tire of a certain type of aircraft. The feasibility of the method is proved by the example.展开更多
The development of new wave energy converters has shed light on a number of unanswered questions in fluid mechanics, but has also identified a number of new issues of importance for their future deployment. The main c...The development of new wave energy converters has shed light on a number of unanswered questions in fluid mechanics, but has also identified a number of new issues of importance for their future deployment. The main concerns relevant to the practical use of wave energy converters are sustainability, survivability, and maintainability. Of course,it is also necessary to maximize the capture per unit area of the structure as well as to minimize the cost. In this review, we consider some of the questions related to the topics of sustainability, survivability, and maintenance access, with respect to sea conditions, for generic wave energy converters with an emphasis on the oscillating wave surge converter. New analytical models that have been developed are a topic of particular discussion. It is also shown how existing numerical models have been pushed to their limits to provide answers to open questions relating to the operation and characteristics of wave energy converters.展开更多
Digital twins have emerged as a promising technology for maintenance applications,enabling organizations to simulate and monitor physical assets to improve their performance.In Operation and Maintenance(O&M),digit...Digital twins have emerged as a promising technology for maintenance applications,enabling organizations to simulate and monitor physical assets to improve their performance.In Operation and Maintenance(O&M),digital twin facilitates the diagnosis and prognosis of critical assets,forming the basis for smart maintenance planning and reducing downtime.However,there is a lack of standardized approaches for the qualifications of digital twins in maintenance,leading to low trustworthiness and limiting its application.This paper proposes a novel framework for the qualifications of digital twins in maintenance based on five pillars,namely fidelity,smartness,timeliness,integration,and standard compliance.We demonstrate the effectiveness of the framework through two case studies,showing how it can be implemented on digital twins for preventive maintenance and condition-based maintenance.Our proposed framework can help organizations across different industrial domains develop and implement digital twins in maintenance more effectively and efficiently,leading to significant benefits in terms of cost reduction,performance improvement,and sustainability.展开更多
The increasing demands of this modern infrastructure require greater structural performance and long-term sustainability while being cost-effective.For a long time,the quest for such construction materials required du...The increasing demands of this modern infrastructure require greater structural performance and long-term sustainability while being cost-effective.For a long time,the quest for such construction materials required durable,intelligent,and cost-effective construction materials.The traditional cementitious materials are very common;however,they have some innate drawbacks:they crack rather easily,cannot self-heal,and lack some damage-monitoring mechanisms for its real-time assessment.Current solutions for structural health monitoring involve extrinsic sensors and wiring that are invasive and costly and do not provide integrated self-healing and damage detection predictivity.This research introduces the work on multi-functional carbon nanotube(CNT)infused smart cement capable of presenting enhanced mechanical performances,in situ damage sensing,and autonomous self-healing capabilities.Key methods used include:1)chemical functionalization of CNT for better dispersion,bonding,and conductivity,which improves mechanical strength by 30% and electrical conductivity 10-fold;2)CNT catalyzing microencapsulated self-healing system:more than 85%crack closure efficiency for cracks up to 0.5 mm;3)three-dimensional printing with CNT infused cement,enabling the creation of complex geometries with embedded sensors,porosity control,and 20%greater structural integrity;4)wireless damage monitoring using CNT-based antennas for crack detection below O.1 mm and signal transmission over 50 m;and 5)artificial intelligence(AI)-enhanced predictive maintenance,achieving a prediction accuracy of 95%-98%in crack propagation and reducing maintenance costs by 30%.This novel integration of functionalized CNT,self-healing agents,wireless sensing,and AI-driven analytics simultaneously strengthens structural integrity while permitting sustainable,non-invasive,and scalable monitoring.What these results indicate is enhanced performance,cost-effectiveness,and longevity,making the technology transformative for the next generations of construction materials.展开更多
文摘A maintenance model is put forward for equipment, which is subjected to internal and external failures. In the model, two maintenance pollcies--perfect minimal repair and replacement are considered. The operational time has a phase type distribution （PH distribution）. Failures＇ arrival follows a Markovian Arrival Process （MAP）. Some failures require the replacement of the system, and others minimal repairs. The performance measures-the mean number of minimal repairs and replacements are analyzed and calculated.
文摘In accordance with the concept of the potential failure of plant, it can be divided into three states: normal, potential failure and functional failure. The intervals of the plant from new to when the potential failure and from potential failure to functional failure are regarded, in this paper, as a random variables. Numerical examples indicate both the nature and sensitivity of the output from the models.
文摘Civil aircraft maintenance process simulation model is an effective method for analyzing the maintainability of a civil aircraft. First, we present the Hierarchical Colored Timed Petri Nets for maintenance process modeling of civil aircraft. Then, we expound a general method of civil aircraft maintenance activities, determine the maintenance level for decomposition, and propose the methods of describing logic of relations between the maintenance activities based on Petri Net. Finally, a time Colored Petri multi-level network modeling and simulation procedures and steps are given with the maintenance example of the landing gear burst tire of a certain type of aircraft. The feasibility of the method is proved by the example.
基金funded by the Science Foundation Ireland (SFI) under the research project “High-end Computational Modelling for Wave Energy Systems” (Grant SFI/10/IN.1/12996) in collaboration with Marine Renewable Energy Ireland (Ma REI)the SFI Centre for Marine Renewable Energy Research (SFI/12/RC/2302)+4 种基金support from EPSRC through Project Grant EP/M021394/1the Sustainable Energy Authority of Ireland (SEAI) through the Renewable Energy Research Development & Demonstration Programme (Grant RE/OE/13/20132074)the European Space Agency (ESA)the numerical simulations were performed on the Stokes and Fionn clusters at the Irish Centre for High-end Computing (ICHEC)the Swiss National Computing Centre under the PRACE-2IP project (Grant FP7 RI-283493)
文摘The development of new wave energy converters has shed light on a number of unanswered questions in fluid mechanics, but has also identified a number of new issues of importance for their future deployment. The main concerns relevant to the practical use of wave energy converters are sustainability, survivability, and maintainability. Of course,it is also necessary to maximize the capture per unit area of the structure as well as to minimize the cost. In this review, we consider some of the questions related to the topics of sustainability, survivability, and maintenance access, with respect to sea conditions, for generic wave energy converters with an emphasis on the oscillating wave surge converter. New analytical models that have been developed are a topic of particular discussion. It is also shown how existing numerical models have been pushed to their limits to provide answers to open questions relating to the operation and characteristics of wave energy converters.
文摘Digital twins have emerged as a promising technology for maintenance applications,enabling organizations to simulate and monitor physical assets to improve their performance.In Operation and Maintenance(O&M),digital twin facilitates the diagnosis and prognosis of critical assets,forming the basis for smart maintenance planning and reducing downtime.However,there is a lack of standardized approaches for the qualifications of digital twins in maintenance,leading to low trustworthiness and limiting its application.This paper proposes a novel framework for the qualifications of digital twins in maintenance based on five pillars,namely fidelity,smartness,timeliness,integration,and standard compliance.We demonstrate the effectiveness of the framework through two case studies,showing how it can be implemented on digital twins for preventive maintenance and condition-based maintenance.Our proposed framework can help organizations across different industrial domains develop and implement digital twins in maintenance more effectively and efficiently,leading to significant benefits in terms of cost reduction,performance improvement,and sustainability.
文摘The increasing demands of this modern infrastructure require greater structural performance and long-term sustainability while being cost-effective.For a long time,the quest for such construction materials required durable,intelligent,and cost-effective construction materials.The traditional cementitious materials are very common;however,they have some innate drawbacks:they crack rather easily,cannot self-heal,and lack some damage-monitoring mechanisms for its real-time assessment.Current solutions for structural health monitoring involve extrinsic sensors and wiring that are invasive and costly and do not provide integrated self-healing and damage detection predictivity.This research introduces the work on multi-functional carbon nanotube(CNT)infused smart cement capable of presenting enhanced mechanical performances,in situ damage sensing,and autonomous self-healing capabilities.Key methods used include:1)chemical functionalization of CNT for better dispersion,bonding,and conductivity,which improves mechanical strength by 30% and electrical conductivity 10-fold;2)CNT catalyzing microencapsulated self-healing system:more than 85%crack closure efficiency for cracks up to 0.5 mm;3)three-dimensional printing with CNT infused cement,enabling the creation of complex geometries with embedded sensors,porosity control,and 20%greater structural integrity;4)wireless damage monitoring using CNT-based antennas for crack detection below O.1 mm and signal transmission over 50 m;and 5)artificial intelligence(AI)-enhanced predictive maintenance,achieving a prediction accuracy of 95%-98%in crack propagation and reducing maintenance costs by 30%.This novel integration of functionalized CNT,self-healing agents,wireless sensing,and AI-driven analytics simultaneously strengthens structural integrity while permitting sustainable,non-invasive,and scalable monitoring.What these results indicate is enhanced performance,cost-effectiveness,and longevity,making the technology transformative for the next generations of construction materials.
