scholarly journals Practical maintenance strategies for teardrop hovering formation relative to elliptical orbit

2021 ◽  
Author(s):  
Shengzhou Bai ◽  
Chao Han ◽  
Xiucong Sun ◽  
Yinrui Rao
Keyword(s):  
Elliptical Orbit ◽  
Maintenance Strategies

scholarly journals Orbit Decomposition Method for Rotordynamic Coefficients Identification of Annular Seals

2021 ◽  
Vol 11 (9) ◽  
pp. 4237
Author(s):  
Mingjie Zhang ◽  
Jiangang Yang ◽  
Wanfu Zhang ◽  
Qianlei Gu
Keyword(s):  
Circular Orbit ◽  
Present Method ◽  
Decomposition Method ◽  
Parameter Analysis ◽  
Elliptical Orbit ◽  
Computational Time ◽  
Solution Technique ◽  
Rotordynamic Coefficients ◽  
Cfd Method ◽  
Annular Seals

The elliptical orbit whirl model is widely used to identify the frequency-dependent rotordynamic coefficients of annular seals. The existing solution technique of an elliptical orbit whirl model is the transient computational fluid dynamics (CFD) method. Its computational time is very long. For rapid computation, this paper proposes the orbit decomposition method. The elliptical whirl orbit is decomposed into the forward and backward circular whirl orbits. Under small perturbation circumstances, the fluid-induced forces of the elliptical orbit model can be obtained by the linear superposition of the fluid-induced forces arising from the two decomposed circular orbit models. Due to that the fluid-induced forces of circular orbit, the model can be calculated with the steady CFD method, and the transient computations can be replaced with steady ones when calculating the elliptical orbit whirl model. The computational time is significantly reduced. To validate the present method, its rotordynamic results are compared with those of the transient CFD method and experimental data. Comparisons show that the present method can accurately calculate the rotordynamic coefficients. Elliptical orbit parameter analysis reveals that the present method is valid when the whirl amplitude is less than 20% of seal clearance. The effect of ellipticity on rotordynamic coefficients can be ignored.

scholarly journals Bayesian maintenance decision optimisation based on computing the information value from condition inspections

2021 ◽  
pp. 1748006X2097812
Author(s):  
Guang Zou ◽  
Kian Banisoleiman ◽  
Arturo González
Keyword(s):  
Decision Making ◽  
Structural Integrity ◽  
Fatigue Cracking ◽  
Cost Effective ◽  
Offshore Structures ◽  
Information Value ◽  
Bayesian Decision ◽  
Maintenance Strategies ◽  
Optimal Maintenance ◽  
Maintenance Decision

A challenge in marine and offshore engineering is structural integrity management (SIM) of assets such as ships, offshore structures, mooring systems, etc. Due to harsh marine environments, fatigue cracking and corrosion present persistent threats to structural integrity. SIM for such assets is complicated because of a very large number of rewelded plates and joints, for which condition inspections and maintenance are difficult and expensive tasks. Marine SIM needs to take into account uncertainty in material properties, loading characteristics, fatigue models, detection capacities of inspection methods, etc. Optimising inspection and maintenance strategies under uncertainty is therefore vital for effective SIM and cost reductions. This paper proposes a value of information (VoI) computation and Bayesian decision optimisation (BDO) approach to optimal maintenance planning of typical fatigue-prone structural systems under uncertainty. It is shown that the approach can yield optimal maintenance strategies reliably in various maintenance decision making problems or contexts, which are characterized by different cost ratios. It is also shown that there are decision making contexts where inspection information doesn’t add value, and condition based maintenance (CBM) is not cost-effective. The CBM strategy is optimal only in the decision making contexts where VoI > 0. The proposed approach overcomes the limitation of CBM strategy and highlights the importance of VoI computation (to confirm VoI > 0) before adopting inspections and CBM.

scholarly journals Fleet Resilience: Evaluating Maintenance Strategies in Critical Equipment

2020 ◽  
Vol 11 (1) ◽  
pp. 38
Author(s):  
Orlando Durán ◽  
Javier Aguilar ◽  
Andrea Capaldo ◽  
Adolfo Arata
Keyword(s):  
Application Study ◽  
System Availability ◽  
Maintenance Strategies ◽  
Resilience Index ◽  
Reliability Block Diagrams ◽  
Maintenance Policies ◽  
Definition Of ◽  
The Impact ◽  
Important System ◽  
Intrinsic Characteristic

Resilience is an intrinsic characteristic of systems. Through it, the capacity of a system to react to the existence of disruptive events is expressed. A series of metrics to represent systems’ resilience have been proposed, however, only one indicator relates the availability of the system to this characteristic. With such a metric, it is possible to relate the topological aspects of a system and the resources available in order to be able to promptly respond to the loss of performance as a result of unexpected events. This work proposes the adaptation and application of such a resilience index to assess the influence of different maintenance strategies and topologies in fleets’ resilience. In addition, an application study considering an actual mining fleet is provided. A set of critical assets was identified and represented using reliability block diagrams. Monte Carlo simulation experiments were conducted and the system availability data were extracted. Resilience indexes were obtained in order to carry out the definition of the best maintenance policies in critical equipment and the assessment of the impact of modifying system redundancies. The main results of this work lead to the overall conclusion that redundancy is an important system attribute in order to improve resiliency along time.

Maintaining Effects of Pulmonary Rehabilitation at Home in Chronic Obstructive Pulmonary Disease: A Systematic Literature Review

2021 ◽  
pp. 108482232199037
Author(s):  
Duarte Pinto ◽  
Lissa Spencer ◽  
Soraia Pereira ◽  
Paulo Machado ◽  
Paulino Sousa ◽  
...  
Keyword(s):  
Chronic Obstructive Pulmonary Disease ◽  
Literature Review ◽  
Pulmonary Rehabilitation ◽  
Rehabilitation Program ◽  
Chronic Obstructive ◽  
Obstructive Pulmonary Disease ◽  
Maintenance Strategies ◽  
Rehabilitation Programs ◽  
Home Based ◽  
Pulmonary Rehabilitation Program

To systematize strategies that may support patients with Chronic Obstructive Pulmonary Disease to maintain the effects of pulmonary rehabilitation over time. This systematic literature review was conducted, and the evidence was electronically searched in the Web of Science, Scopus, and EBSCO databases. This review included randomized controlled clinical trials, published until September 2019, that addressed components of an unsupervised home-based pulmonary rehabilitation program, maintenance strategies following outpatient pulmonary rehabilitation programs, as well as data on outcomes for quality of life, exercise performance, and dyspnea. A final sample of 5 articles was obtained from a total of 1693 studies. Data for final synthesis were grouped into 2 categories: components of unsupervised home-based pulmonary rehabilitation programs and maintenance strategies. An unsupervised home-based pulmonary rehabilitation program should consist of an educational component, an endurance training component, and a strength training component. When patients are transferred to the home environment, it is important to include more functional exercises specifically adapted to the patient’s condition, goals, and needs.

scholarly journals Special Issue “Advances in Machine Learning and Deep Learning Based Machine Fault Diagnosis and Prognosis”

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 532
Author(s):  
Mohand Djeziri ◽  
Marc Bendahan
Keyword(s):  
Machine Learning ◽  
Deep Learning ◽  
Fault Diagnosis ◽  
Special Issue ◽  
Maintenance Strategies ◽  
Corrective Maintenance ◽  
Diagnosis And Prognosis ◽  
Machine Fault Diagnosis ◽  
Failure Prognosis ◽  
Fault Diagnosis And Prognosis

Fault diagnosis and failure prognosis aim to reduce downtime of the systems and to optimise their performance by replacing preventive and corrective maintenance strategies with predictive or conditional ones [...]

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