•Investigation of the relationship among the different maintenance related concepts and their evolutionary path.•We aim to define the concept of advanced maintenance, based on the state of the art of ...research and empirical evidence of practices.•Research methods are systematic literature review, bibliometric analysis and multiple case study involving production companies.•Advanced Maintenance is recognized as an approach inheriting the knowledge from past developments of maintenance related concepts.
The implementation of Industry 4.0-like solutions for the maintenance of production assets is a relevant topic in the mainstream for researchers and industries around the world. As a matter of facts, the technology-based transformation of maintenance has been germinated since several years. In fact, the evolution of maintenance along with the development of the information and communication technologies has been studied in the literature since early 2000, and concepts like e-maintenance and intelligent maintenance have been largely addressed. Nowadays, smart maintenance and maintenance 4.0 concepts are getting popular in the Industry 4.0-based literature. While e-maintenance, intelligent maintenance, smart maintenance and maintenance 4.0 are similar concepts, they are not identical. From an evolutionary perspective, there has been little consideration on whether the definition, connotation, and technical development of the concepts are consistent in the literature. To address this gap, the work performs a qualitative and quantitative investigation of the scientific literature to clarify the relationship among the different maintenance concepts. A bibliometric analysis of publication sources, annual publication numbers, keywords frequency, and top regions of research and development establishes the scope and trends of the currently presented research. Critical topics discussed include the evolutionary path of the different concepts. Moreover, the evidence collected through a case study involving eight production companies are discussed to report the perspective of industry about advanced maintenance, may it be defined 4.0, smart, intelligent or e-maintenance. Finally, a definition of the advanced maintenance concept is given, proposed as an integral approach inheriting the knowledge from past developments of e-maintenance and intelligent maintenance concepts and more recent developments including smart maintenance and maintenance 4.0.
The protein mini-chromosome maintenance 10 (Mcm10) was originally identified as an essential yeast protein in the maintenance of mini-chromosome plasmids. Subsequently, Mcm10 has been shown to be ...required for both initiation and elongation during chromosomal DNA replication. However, it is not fully understood how the multiple functions of Mcm10 are coordinated or how Mcm10 interacts with other factors at replication forks. Here, we identified and characterized the Mcm2–7-interacting domain in human Mcm10. The interaction with Mcm2–7 required the Mcm10 domain that contained amino acids 530–655, which overlapped with the domain required for the stable retention of Mcm10 on chromatin. Expression of truncated Mcm10 in HeLa cells depleted of endogenous Mcm10 via siRNA revealed that the Mcm10 conserved domain (amino acids 200–482) is essential for DNA replication, whereas both the conserved and the Mcm2–7-binding domains were required for its full activity. Mcm10 depletion reduced the initiation frequency of DNA replication and interfered with chromatin loading of replication protein A, DNA polymerase (Pol) α, and proliferating cell nuclear antigen, whereas the chromatin loading of Cdc45 and Pol ϵ was unaffected. These results suggest that human Mcm10 is bound to chromatin through the interaction with Mcm2–7 and is primarily involved in the initiation of DNA replication after loading of Cdc45 and Pol ϵ.
The selective maintenance problem (SMP) arises in many mission-oriented multi-component systems that are operated for consecutive missions interspersed with finite breaks, during which only limited ...component repairs can be performed due to constrained resources. This NP-hard problem decides which components to maintain and to what levels of repair to guarantee a pre-specified performance level during the subsequent mission. Over the last two decades, a sizeable body of literature has been published on this topic. However, the contributions have stagnated in quality, and most articles deal with small to moderate problems. This paper provides a critical review of the SMP literature. A total of 136 research articles related to SMP are reviewed and a selection of key representative models is discussed in detail. This review is framed according to two feature categories: formulation characteristics, composed of three sub-groups of characteristics related to the system, maintenance and mathematical model characteristics; and solution approaches, grouped by exact methods and approximate algorithms. This critical review is aimed at identifying drawbacks, shortcomings, and blind spots of the SMP literature, and providing a roadmap for the challenges to be addressed and innovative future research topics to further advance the academic and industrial contributions of SMP.
•Consider joint optimization of imperfect inspection and replacement decisions•Discretely formulate a continuous degradation process and observations•Propose an integrated quality-cost based ...imperfect inspection model•Develop a cost model integrating both inspection and maintenance•Compare the performance of different maintenance and inspections policies
The quality of condition monitoring is an important factor affecting the effectiveness of a condition-based maintenance program. It depends closely on implemented inspection and instrument technologies, and eventually on investment costs, i.e., a more accurate condition monitoring information requires a more sophisticated inspection, hence a higher cost. While numerous works in the literature have considered problems related to condition monitoring quality, (e.g., imperfect inspection models, detection and localization techniques, etc.) few of them focus on adjusting condition monitoring quality for condition-based maintenance optimization. In this paper, we investigate how such an adjustment can help to reduce the total cost of a condition-based maintenance program. The condition monitoring quality is characterized by the observation noises on the system degradation level returned by an inspection. A dynamic condition-based maintenance and inspection policy adapted to such a observation information is proposed and formulated based on Partially Observable Markov Decision Processes. The use and advantages of the proposed joint inspection and maintenance model are numerically discussed and compared to several inspection-maintenance policies through numerical examples.
Summary Until recently, the association of chronic insomnia with significant medical morbidity was not established and its diagnosis was based solely on subjective complaints. We present evidence ...that insomnia with objective short sleep duration is the most biologically severe phenotype of the disorder, as it is associated with cognitive-emotional and cortical arousal, activation of both limbs of the stress system, and a higher risk for hypertension, impaired heart rate variability, diabetes, neurocognitive impairment, and mortality. Also, it appears that objective short sleep duration is a biological marker of genetic predisposition to chronic insomnia. In contrast, insomnia with objective normal sleep duration is associated with cognitive-emotional and cortical arousal and sleep misperception but not with signs of activation of both limbs of the stress system or medical complications. Furthermore, the first phenotype is associated with unremitting course, whereas the latter is more likely to remit. We propose that short sleep duration in insomnia is a reliable marker of the biological severity and medical impact of the disorder. Objective measures of sleep obtained in the home environment of the patient would become part of the routine assessment of insomnia patients in a clinician's office setting. We speculate that insomnia with objective short sleep duration has primarily biological roots and may respond better to biological treatments, whereas insomnia with objective normal sleep duration has primarily psychological roots and may respond better to psychological interventions alone.
•A semi-dynamic OM policy is proposed for multi-station series systems in MSSB production.•It combines the advantages of the opportunity-window-based policy and the dynamic policy.•A constant MTW is ...defined firstly to decrease the complexity of the solution space.•The OM scheme is obtained on the constant MTW and the dynamic production environment.•For this OM policy, the probability to achieve a better performance is close to 90%.
This paper proposes a new semi-dynamic Opportunistic Maintenance (OM) policy for multi-station series systems, with considering the changing production environment brought by the multi-specification and small-batch production mode. It combines the advantages of the time-window-based OM policy, which can decrease the complexity of the solution space for PM grouping, and the dynamic OM policy, which is capable of adapting to the changing production environment. Whenever one of the stations reaches its original Preventive Maintenance (PM) moment, an OM decision cycle of the system begins. During this decision cycle, all the stations, whose original PM moments are within the presented dynamic Maintenance Time Window (MTW), form a PM group. This dynamic MTW is different for each station, and it is obtained based on the predetermined static MTW and the dynamic impacts from the current production task. The static MTW is constant, and it is derived according to the expected production plan without considering the changing production environment. To balance the maintenance cost for the obtained PM group, the PM is not performed right at the time when one of the stations reaches its original PM moment, and it is postponed. The optimal duration of the postponement is dynamically obtained by minimizing the total maintenance cost within this duration. Finally, numerical examples and comparisons are illustrated to show the effectiveness of the proposed semi-dynamic OM policy.
As the offshore wind farm (OWF) is often difficult to access due to weather restrictions, the scheduling strategy of operation and maintenance (O&M) becomes a highly complex task. This study presents ...an O&M scheduling strategy model considering the priority of O&M task and practise constraints of O&M scheduling. First, the two-stage maintenance division method is introduced to consider the priority of O&M task. The initial division of wind turbines to be maintained is obtained by considering operation status. The second-stage maintenance division considering the available maintenance resources is formed adopting the cluster analysis, which the warning and delayed maintenance wind turbines have become a priority. Then, the practise constraints such as the O&M vessels, technicians, daily working time, maintenance route and others are taken into account in the O&M task scheduling model. The proposed model aims to provide the optimal sequence and routeing of maintenance task such that the maintenance scheduling cost is minimised. Simulation results in the scheduling of O&M task for an OWF confirm the feasibility of the proposed model. Sensitivity analysis is undertaken with respect to daily maintenance time, vessel and technician configuration and weather condition.
•A Weibull proportional hazards model is adopted to model the hazard rate of the hard failure.•The degradation level is treated as a multiplicative time-varying covariate.•The closed-form of the RUL ...distribution is derived based on the Brownian bridge theory.•The optimal maintenance schedule is updated when new degradation signals are available.
The remaining useful lifetime (RUL) estimated from the in-situ degradation data has shown to be useful for online predictive maintenance. In the literature, the RUL is often estimated by assuming a soft-failure threshold for the degradation data. In practice, however, systems may not be subject to the degradation-induced soft failures. Instead, the systems are deemed to be fail when they cannot perform the intended function, and such failures are known as hard failures. Because there are no fixed thresholds for hard failures, the corresponding RUL estimation is not an easy task, which causes difficulties in finding the optimal maintenance schedule. In this study, a Weibull proportional hazards model is proposed to jointly model the degradation data and the failure time data. The degradation data are treated as the time-varying covariates so that the degradation does not directly lead to system failures, but increases the hazard rate of hard failures. A random-effects Wiener process is proposed to model the degradation data by considering the system heterogeneities. Based on the developed proportional hazards model, closed-form distribution of the RUL is derived upon each inspection and the optimal maintenance schedule is then obtained by minimizing the system maintenance cost. The proposed maintenance strategy is successfully applied to predictive maintenance of lead-acid batteries.
The purpose of this paper is to investigate the maintenance practices that are used in Swedish industry. The study was performed by conducting a cross-sectional survey within Swedish firms that have ...at least 100 employees. The main results achieved from the study show that the role of maintenance is not highly recognised. There is a need to spend and invest more in maintenance, which is considered by the majority of Swedish industries as a necessary expense. Although about 13% of the maintenance department time is spent on planning maintenance tasks, nevertheless, about one third of the time is spent on unplanned tasks. There is a need for more adoption of maintenance concepts such as total productive maintenance (TPM) and reliability-centred maintenance (RCM). The lack or ineffectiveness of planning and scheduling can significantly restrict the maintenance department in achieving its objectives and can thus prevent the company from maximising business profits and offering competitive advantages.
We develop a stochastic optimization framework for integrated condition-based maintenance and operations scheduling for a fleet of generators with explicit consideration of unexpected failures. Our ...approach is based on a model that uses condition-based failure scenarios derived from the remaining lifetime distributions of the generators, as well as a chance constraint to ensure a reliable maintenance plan. We derive a deterministic safe approximation of the difficult chance constraint. The large number of failure scenarios is handled by a combination of sample average approximation and an enhanced scenario decomposition algorithm in a distributed framework. We introduce a number of algorithmic improvements by exploiting the polyhedral structure of the problem, utilizing its time decomposability, and an analysis of the transmission line capacities. Finally, we present a case study demonstrating the significant cost savings and computational benefits of the proposed framework.
PDF
