Dynamic Maintenance Research Articles

Dynamic Opportunistic Maintenance Model of Multi-Component System Considering Degradation Interaction

Dynamic Opportunistic Maintenance Model of Multi-Component System Considering Degradation Interaction

Wnt10b-GSK3β-dependent Wnt/STOP signaling prevents aneuploidy in human somatic cells.

Wnt signaling is crucial for proper development, tissue homeostasis and cell cycle regulation. A key role of Wnt signaling is the GSK3β-mediated stabilization of β-catenin, which mediates many of the critical roles of Wnt signaling. In addition, it was recently revealed that Wnt signaling can also act independently of β-catenin. In fact, Wnt mediated stabilization of proteins (Wnt/STOP) that involves an LRP6-DVL-dependent signaling cascade is required for proper regulation of mitosis and for faithful chromosome segregation in human somatic cells. We show that inhibition of Wnt/LRP6 signaling causes whole chromosome missegregation and aneuploidy by triggering abnormally increased microtubule growth rates in mitotic spindles, and this is mediated by increased GSK3β activity. We demonstrate that proper mitosis and maintenance of numerical chromosome stability requires continuous basal autocrine Wnt signaling that involves secretion of Wnts. Importantly, we identified Wnt10b as a Wnt ligand required for the maintenance of normal mitotic microtubule dynamics and for proper chromosome segregation. Thus, a self-maintaining Wnt10b-GSK3β-driven cellular machinery ensures the proper execution of mitosis and karyotype stability in human somatic cells.

Cancerous pericarditis presenting as cardiac tamponade in a 68-year-old man with pancreatic adenocarcinoma: a case report

IntroductionPericardial effusion is a rare complication of pancreatic cancer. We report a case of cardiac tamponade secondary to pancreatic cancer.Case presentationA 68-year-old Japanese man was diagnosed as having pancreatic cancer during surgery and received chemotherapy for 28 months after the diagnosis. He was admitted to the emergency room with severe dyspnea. Echocardiography revealed pericardial effusion with severe hypofunction. Emergency pericardial drainage was performed to maintain hemodynamics, which resulted in the elimination of 450 mL of blood and the maintenance of circulatory dynamics. Cytological examination of the pericardial fluid revealed atypical cells and tumor cells suggesting adenocarcinoma.ConclusionsTo our knowledge, pancreatic cancer complicated with cancerous pericarditis has not been previously documented. This case highlights the extreme severity of pericardial effusion, a sign of progressive disease, secondary to pancreatic cancer. In the case of neoplastic pericardial effusion, an extremely poor prognosis must be considered.

A preventive maintenance policy with usage-dependent failure rate thresholds under two-dimensional warranties

This article considers Preventive Maintenance (PM) under a two-dimensional (2-D) warranty contract with time and usage limits. From a manufacturer’s point of view, we develop a dynamic maintenance model with a random horizon to include the impact of random and dynamic usage rates on PM decisions. The model treats the cumulative amount of usage as a state variable that provides information about the failure rate and the expiration of the 2-D warranty. We characterize the optimal PM policy by a sequence of usage-dependent failure rate thresholds. Each threshold is a function of the cumulative usage. Our failure rate threshold policy chooses one of the following two actions in each period: performing perfect PM or no PM. Specifically, the manufacturer should bring the failure rate back to its original level when it exceeds the threshold in the corresponding period. This policy is also optimal under a constant usage rate. In the numerical experiments, we demonstrate the effectiveness of the proposed policy and conduct a sensitivity analysis to investigate how this policy is affected by the model parameters.

Research on Wireless Ad Hoc Network Technology for Building Monitoring

Aiming at the difficulties of equipment expansion, high data collection cost, and difficulty in data sharing faced by traditional building monitoring systems, this paper proposes a wireless ad hoc network technology for building monitoring. This method establishes a wireless ad hoc network through wireless network structure selection, wireless network self-organization and dynamic maintenance. Experimental results show that the wireless ad hoc network technology greatly reduces the cost of networking and debugging of intelligent systems, and can well meet the needs of intelligent monitoring of existing traditional buildings.

Reliability analysis and dynamic maintenance model based on fuzzy degradation approach

The rapid growth of population density and people demand based on railway services increases day by day. Hence, the maintenance (i.e., degradation and aging) and the decision-making processes of rail wheels are troublesome. There has been an impact of degradation stage for a system such as a repair, replacement, and inspection time. In this paper, an adaptive neural-based fuzzy inference system (ANFIS) rail wheel maintenance model is proposed using the modified spider monkey algorithm, with the parametric update. As the design of the wheel maintenance strategy, the degradation stage increases with system aging and it can be minimized using repair. In this way, this article presents the development of system reliability that is dealing with the establishment of a maintenance strategy. A higher running cost rate reduces the main contribution of the reparation cycle using an optimum maintenance model, and the locomotive wheels are employed to demonstrate the efficiency of the proposed methodology. Under optimal inspection time, the impact of system failures such as aging and degradation is determined successfully. The proposed model can able to identify the precise time when rail tracks fail to minimize the maintenance cost/time. This ANFIS and MSMA can increase the efficiency of maintenance activities and decrease the cost of maintenance in the long term. Similarly, the results demonstrate that the proposed maintenance model is more flexible, and the capability of gauge value prediction using real and estimated values is accurate.

Seasonal hydrology and fish assemblage structure in the floodplain of the lower Amazon River

AbstractWe investigated how the taxonomic and functional structures of fish assemblages in the lower Amazon River floodplain responded to seasonal hydrological variations. Fishes were sampled in 440 aquatic habitats across a floodplain area of 17,673 km2 during periods of high, receding, low and rising water. In addition, we recorded local environmental and landscape variables known to affect fish assemblages in floodplains. Redundancy analysis indicated that the taxonomic and functional structures of the fish assemblages were associated with water levels as well as local environmental, landscape and spatial variables. Our results showed that piscivores, planktivores and omnivores, as well as species with periodic and intermediate life history strategies, dominated the floodplain fish assemblages during periods of high‐water levels, whereas herbivores, invertivores and detritivores, as well as species of large body size with an equilibrium life history strategy, dominated the fish assemblages during periods of low‐water levels. Hydrology strongly influenced the structure of the fish assemblages in the Amazon floodplains. Our results indicate that the maintenance of seasonal hydrological dynamics in the basin is essential for the conservation of the regional fish diversity.

Earthworms accelerate rice straw decomposition and maintenance of soil organic carbon dynamics in rice agroecosystems.

BackgroundTo promote straw degradation, we inoculated returned farmland straw with earthworms (Pheretima guillelmi). Increasing the number of earthworms may generally alter soil organic carbon (SOC) dynamics and the biological activity of agricultural soils.MethodsWe performed soil mesocosm experiments with and without earthworms to assess the decomposition and microbial mineralization of returned straw and soil enzyme activity across different time periods.ResultsWhen earthworms were present in soil, the surface residues were completely consumed during the first four weeks, but when earthworms were absent, most of the residues remained on the soil surface after 18 weeks. On day 28, the SOC content was significantly higher in the treatment where both earthworms and residue had been added. The SOC content was lower in the treatment where earthworms but no residue had been added. The organic carbon content in water-stable macroaggregates showed the same trend. During the first 14 weeks, the soil basal respiration was highest in the treatments with both residues and earthworms. From weeks 14 to 18, basal respiration was highest in the treatments with residues but without earthworms. We found a significant positive correlation between soil basal respiration and soil dissolved organic carbon content. Earthworms increased the activity of protease, invertase, urease and alkaline phosphatase enzymes, but decreased β-cellobiohydrolase, β-glucosidase and xylosidase activity, as well as significantly reducing ergosterol content.ConclusionThe primary decomposition of exogenous rice residues was mainly performed by earthworms. Over a short period of time, they converted plant carbon into soil carbon and increased SOC. The earthworms played a key role in carbon conversion and stabilization. In the absence of exogenous residues, earthworm activity accelerated the decomposition of original organic carbon in the soil, reduced SOC, and promoted carbon mineralization.

The Maintenance of Mitochondrial DNA Integrity and Dynamics by Mitochondrial Membranes.

Mitochondria are complex organelles that harbour their own genome. Mitochondrial DNA (mtDNA) exists in the form of a circular double-stranded DNA molecule that must be replicated, segregated and distributed around the mitochondrial network. Human cells typically possess between a few hundred and several thousand copies of the mitochondrial genome, located within the mitochondrial matrix in close association with the cristae ultrastructure. The organisation of mtDNA around the mitochondrial network requires mitochondria to be dynamic and undergo both fission and fusion events in coordination with the modulation of cristae architecture. The dysregulation of these processes has profound effects upon mtDNA replication, manifesting as a loss of mtDNA integrity and copy number, and upon the subsequent distribution of mtDNA around the mitochondrial network. Mutations within genes involved in mitochondrial dynamics or cristae modulation cause a wide range of neurological disorders frequently associated with defects in mtDNA maintenance. This review aims to provide an understanding of the biological mechanisms that link mitochondrial dynamics and mtDNA integrity, as well as examine the interplay that occurs between mtDNA, mitochondrial dynamics and cristae structure.

Social inequalities, sexual tourism and HIV in Cartagena, Colombia: an ethnographic study

BackgroundCartagena, Colombia’s main port on the Caribbean Coast, reported an HIV incidence of 7.5 per 100,000 inhabitants in 2007 with 90.0% transmission by heterosexual contact and 70 identified as women with a stable partner. Studies across Colombia illustrate that HIV infection relates to social inequalities; most people with HIV live in poverty and have minimal access to health care, education, and secure jobs. The purpose of this article is to analyse the relationship between social inequalities, sexual tourism and HIV infection in Cartagena, Colombia.MethodsData come from a five-year participatory ethnography of HIV in Cartagena in the period 2004–2009, in which 96 citizens (30 of whom were living with HIV) participated in different data collection phases. Techniques included participant observation, in-depth interviews and thematic life histories. Out of this material, we selected three life histories of two women and a man living with HIV that are representative of the ways in which participants expressed how social inequalities make it virtually impossible to engage in safe sex practices.ResultsAt stake is the exchange of condomless sex for goods within the widespread sexual tourism networks that promote an idealisation of dark-skinned men and women as better sexual performers. Our results illustrate the complex interplay of social inequalities based on class, skin colour, gender and sexual orientation. Furthermore, they suggest a synergistic effect between poverty, racialization, and gender inequalities in the historical maintenance of social dynamics for a fruitful growth of a sexual tourism industry that in turn increases vulnerability to HIV infection.ConclusionsAlthough the convergence of social inequalities has been thoroughly reported in the literature on social studies of HIV vulnerability; distinctive dynamics are occurring in Cartagena, including a clear link between the contemporary globalised sexual tourism industries and a racialised social structure - both having historical roots in the colonial past-.

Seed dispersal by Neotropical bats in human-disturbed landscapes

Abstract In human-modified landscapes, where large bird and mammal species are often functionally extinct, bats are the main seed dispersers. However, the role of seed dispersal by bats for the maintenance of habitat dynamics in fragmented landscapes is still not understood, with information lacking on landscape-level effects of plant–bat interactions. We present some key topics related to spatial ecology of bats and discuss the potential influence of habitat fragmentation on several aspects of seed dispersal by Neotropical bats. We suggest that future studies need to evaluate bat–plant networks along habitat-loss and fragmentation gradients at the landscape level, including changes in land-cover types and habitat structural complexity, going beyond patch-based analysis. By advancing on the comprehension of ecosystem functioning in fragmented landscapes, we will better understand the bat-modulated seed-dispersal process, supporting regeneration and restoration programs that benefit from bat-based functions.

Preliminary design of a management maintenance model of sensitive engineering assets, for a ship under the concept of reliability engineering

The objective of this research is to apply a dynamic maintenance model to the assets of the engineering department of a navy vessel, based on the concept of reliability engineering, which analyzes the statistics of failures of different equipment, in a period of 140 months, in order to determine which is the most sensible equipment, the failure modes and the impact it produces on the ship’s platform. This way, it is possible to focus on the problems that produce the biggest impact in the capacity of the Unit´s, in order to fulfill its roles, and this way, contribute increase its availability. This is an iterative process of continuous improvement for the maintenance plans.

Risk analysis for lot-sizing and maintenance optimization problem under energy constraint with subcontractor solution

PurposeThe main contribution of this manuscript is to suggest new approaches in order to deal with dynamic lot-sizing and maintenance problem under aspect energetic and risk analysis. The authors introduce a new maintenance strategy based on the centroid approach to determine a common preventive maintenance plan for all machines to minimize the total maintenance cost. Thereafter, the authors suggest a risk analysis study further to unforeseen disruption of availability machines with the aim of helping the production stakeholders to achieve the obtained forecasting lot-size plan.Design/methodology/approachThe authors tackle the dynamic lot-sizing problem using an efficient hybrid approach based on random exploration and branch and bound method to generate possible solutions. Indeed, the feasible solutions of random exploration method are used as input for branch and bound to determine the near-optimal solution of lot-size plan. In addition, our contribution to the maintenance part is to determine the optimal common maintenance plan for M machines based on a new algorithm called preventive maintenance (PM) periods means.FindingsFirst, the authors have funded the optimal lot-size plan that should satisfy the random demand under service level requirement and energy constraint while minimizing the costs of production and inventory. Indeed, establishing a best lot-size plan is to determine the appropriate number of available machines and manufactured units per period. Second, for risk analysis study, the solution of subcontracting is proposed by specifying a maximum cost of subcontractor in the context of a calling of tenders.Originality/valueFor maintenance problem, the originality consists in regrouping the maintenance plans of M machines into only one plan. This approach lets us to minimize the total maintenance cost and reduces the frequent breaks of production. As a second part, this paper contributed to the development of a new risk analysis study further to unforeseen disruption of availability machines. This risk analysis developed a decision-making system, for production stakeholders, in order to achieve the forecasting lot-size plan and keeps its profitability, by specifying the unit cost threshold of subcontractor in the context of a calling of tender.

Optimal maintenance decisions for deteriorating quoin blocks in miter gates subject to uncertainty in the condition rating protocol

Condition assessments and rating systems are frequently used by field engineers to assess inland navigation assets and components. The goal of these assessments is to initiate effective risk-informed budget plans for maintenance and repair/replace. Ideally, a degradation model of every component failure mode in the gate would facilitate maintenance decision-making. However, sometimes there is no clear physical understanding how a damage progresses in time; for example, it isn't clear how the bearing gaps change in time in the quoin blocks of a miter gate. Therefore, this is one motivation for the framework proposed in this paper, which integrates Structural Health Monitoring with a Markov transition matrix built from historical condition assessment. To show the applicability of this framework, two examples are presented of how to find the optimal time to plan for maintenance of components in miter gates i) static maintenance planning based on operational condition assessment (OCA) ratings only and ii) dynamic maintenance planning based on integration of damage diagnostics based on monitoring data and failure prognosis based on OCA ratings. In addition, this paper presents a new Bayesian approach to estimate the ratio of errors in the OCA ratings, which allows for improved accuracy in OCA rating-based prognosis.

Dynamic maintenance based on functional usage profiles

PurposeFor many decades, it has been recognized that maintenance activities should be adapted to the specific usage of a system. For that reason, many advanced policies have been developed, such as condition-based and load-based maintenance policies. However, these policies require advanced monitoring techniques and rather detailed understanding of the failure behavior, which requires the support of an OEM or expert, prohibiting application by an operator in many cases. The present work proposes a maintenance policy that relieves the high (technical) demands set by these existing policies and provides a more accurate specification of the required (dynamic) maintenance interval than traditional usage-based maintenance.Design/methodology/approachThe methodology followed starts with a review and critical assessment of existing maintenance policies, which are classified according to six different aspects. Based on the need for a technically less demanding policy that appears from this comparison, a new policy is developed. The consecutive steps required for this functional usage profiles based maintenance policy are then critically discussed: usage profile definition, monitoring, profile severity quantification and the possible extension to the fleet level. After the description of the proposed policy, it is demonstrated in three case studies on real systems.FindingsA maintenance policy based on a simple usage registration procedure appears to be feasible, which enables a significantly more efficient maintenance process than the traditional usage-based policies. This is demonstrated by the policy proposed here.Practical implicationsThe proposed maintenance policy based on functional usage profiles offers the operators of fleets of systems the opportunity to increase the efficiency and effectiveness of their maintenance process, without the need for a high investment in advanced monitoring systems and in experts interpreting the results.Originality/valueThe original contribution of this work is the explicit definition of a new maintenance policy, which combines the benefits of considering the effects of usage or environment severity with a limited investment in monitoring technology.

Dynamic maintenance planning of a hydro-turbine in operational life cycle

Life cycle assessment (LCA) has been an emerging feature of modern structural health monitoring techniques that aims at evaluating equipment degradation process and it can be used for development of dynamic maintenance plans. A novel framework based on LCA is proposed in this paper for dynamic maintenance planning of hydro-turbines. Using a Hidden Markov Model (HMM) and the inspection data of hydro-turbine runner cracks from actual operations, the transition probability matrix and sojourn time of different crack states are obtained. This is utilized for predicting the expected remaining useful life (RUL) and the formulation of maintenance intervals. Moreover, maintenance plans are developed from the influence of cracks in different states leading to critical conditions. The proposed method, as demonstrated in the case study, efficiently updates the maintenance intervals and reduces the likelihood of failure events. The results of this paper provide a valid maintenance framework for achieving higher operational safety of hydropower stations with minimal resource losses.

Tristage Bargaining Dynamic Game-Based Preventive Maintenance for Electric Multiple Unit

The operation and maintenance sectors of electric multiple unit (EMU) are considered as game participants to optimize the preventive maintenance (PM) schedule of EMU components. The total cost of a component over a life cycle includes failure risk and maintenance cost. The failure risk of EMU components is assessed quantitatively by using an analytic hierarchy process and scoring and weighting the factors that affect the failure risk of such components. The operation sector expects failure risk to be minimized, whereas the maintenance sector expects maintenance costs to be low, and their interests interfere with each other to some extent. This study establishes a tristage bargaining dynamic game model of the operation sector priority bid and maintenance sector priority bid considering the PM reliability threshold R as the bargaining object. A numerical example demonstrates that the result is more beneficial to the sector that bids first, and the operation priority bid allows the component to maintain a higher reliability level over a life cycle, especially in the latter half of the component life cycle.

Dynamic Optimization for Airline Maintenance Operations

The occurrence of unexpected aircraft maintenance tasks can produce expensive changes in an airline’s operation. When it comes to critical tasks, it might even cancel programmed flights. Despite this, the challenge of scheduling aircraft maintenance operations under uncertainty has received limited attention in the scientific literature. We study a dynamic airline maintenance scheduling problem, which daily decides the set of aircraft to maintain and the set of pending tasks to execute in each aircraft. The objective is to minimize the expected costs of expired maintenance tasks over the operating horizon. To increase flexibility and reduce costs, we integrate maintenance scheduling with tail assignment decisions. We formulate our problem as a Markov decision process and design dynamic policies based on approximate dynamic programming, including value function approximation, rolling horizon techniques, and a hybrid policy between the latter two that delivers the best results. In a case study based on LATAM airline, we show the value of dynamic optimization by testing our best policies against a simple airline decision rule and a deterministic relaxation with perfect future information. We suggest to schedule tasks requiring less resources first to increase utilization of residual maintenance capacity. Finally, we observe strong economies of scale when sharing maintenance resources between multiple airlines.

A heuristic policy for maintaining multiple multi-state systems

This work is concerned with the optimal allocation of limited maintenance resources among a collection of competing multi-state systems, and the dynamic of each multi-state system is modelled by a Markov chain. Determining the optimal dynamic maintenance policy is prohibitively difficult, and hence we propose a heuristic dynamic maintenance policy in which maintenance resources are allocated to systems with higher importance. The importance measure is well justified by the idea of subsidy, yet the computation is expensive. Hence, we further propose two modifications of the importance measure, resulting in two modified heuristic policies. The performance of the two modified heuristics is evaluated in a systematic computational study, showing exceptional competence.

Dynamic study of critical factors of explosion accident in laboratory based on FTA

Laboratory safety has been widely concerned, but fire, explosion, poisoning and other accidents occur from time to time. Among them, the proportion of safety accidents, casualties and economic losses caused by explosion are relatively high. In particular, the safety, reliability and maintainability of laboratories in colleges and universities and scientific research institutes should be evaluated and optimized. Therefore, it is necessary to use efficient, reliable and economical methods to identify and monitor the key factors that will cause explosion accidents in the laboratory. In this paper, through the combination of fault tree analysis (FTA) and binary decision diagram (BDD), the three main sources of explosion accidents in laboratory (gas cylinder, pressure device and hazardous chemicals) are analyzed quantitatively. When using BDD to simplify FT operation, a variety of event sorting methods are compared. Finally, it is found that “Level” and “AND” methods can provide a more convenient and reasonable number of cut sets. Considering different methods to measure the importance of basic events, it is found that similar results can be obtained. The importance of Critical is used to identify the importance of events, combined with its change with time, the change of importance is analyzed dynamically. The key factors from four aspects of “human”, “machine”, “environment” and “management” in laboratory explosion accident are determined. It provides a new idea for the dynamic safety management and maintenance of the laboratory, and puts forward some ideas for the new research content at the end of this paper.