scholarly journals Importance measure-based maintenance strategy considering maintenance costs

2021 ◽  
Vol 24 (1) ◽  
pp. 15-24
Author(s):  
Chao Zhang ◽  
Yadong Zhang ◽  
Hongyan Dui ◽  
Shaoping Wang ◽  
Mileta M. Tomovic
Keyword(s):  
Preventive Maintenance ◽  
System Performance ◽  
Maintenance Cost ◽  
Importance Measure ◽  
Repairable Systems ◽  
Consistent System ◽  
System Components ◽  
System Maintenance ◽  
The Difference ◽  
Selection Of

Maintenance is an important way to ensure the best performance of repairable systems. This paper considers how to reduce system maintenance cost while ensuring consistent system performance. Due to budget constraints, preventive maintenance (PM) can be done on only some of the system components. Also, different selections of components to be maintained can have markedly different effects on system performance. On the basis of the above issues, this paper proposes an importance-based maintenance priority (IBMP) model to guide the selection of PM components. Then the model is extended to find the degree of correlation between two components to be maintained and a joint importance-based maintenance priority (JIBMP) model to guide the selection of opportunistic maintenance (OM) components is proposed. Also, optimization strategies under various conditions are proposed. Finally, a case of 2H2E architecture is used to demonstrate the proposed method. The results show that generators in the 2E layout have the highest maintenance priority, which further explains the difference in the importance of each component in PM.

Variations in Composition and Rheology of Bituminous Crack Sealants for Pavement Maintenance

2005 ◽  
Vol 1933 (1) ◽  
pp. 107-112 ◽  
Author(s):  
J.-F. Masson ◽  
Peter Collins ◽  
Sladana Bundalo-Perc ◽  
John R. Woods ◽  
Imad Al-Qadi
Keyword(s):  
Asphalt Concrete ◽  
Preventive Maintenance ◽  
Field Performance ◽  
Concrete Pavements ◽  
Past Performance ◽  
Pavement Maintenance ◽  
The Difference ◽  
And Performance ◽  
Over Time ◽  
Selection Of

Bituminous crack sealants are used for the preventive maintenance of asphalt concrete pavements. The selection of a durable sealant can be difficult, however, mainly because of the lack of correlation between standard sealant specifications and field performance. Hence, an approved list of materials based on past performance is sometimes used to select sealants. However, sealant durability and performance vary over time. To investigate the effect of sealant lot variation on sealant properties, six lots of two sealants from different suppliers were analyzed for filler and polymer contents and rheological response. It was found that the difference in composition and rheology between lots can be similar to that between sealants produced by different manufacturers. Hence, sealant lot-to-lot variation can partly explain the variation in the field performance of sealants. Therefore, lists of approved products drawn from the field performance of past years are ineffective in the selection of sealants for future maintenance. The application of segregated sealants was also investigated, including assessing the effect of melter stirring on sealant homogeneity and measuring the segregation of sealant upon cooling. It was found that sealants do not segregate after their application and subsequent cooling and that a rapid circumferential stirring of 25 revolutions per minute in the heating kettle allowed for the remixing of a segregated sealant.

An optimal preventive maintenance strategy for the hydraulic system of platform firefighting vehicle based on the improved NSGA-II algorithm

2019 ◽  
Vol 233 (6) ◽  
pp. 978-989 ◽  
Author(s):  
Rumin Teng ◽  
Jifei Liang ◽  
Guanglei Wu ◽  
Dianlong Wang ◽  
Xin Wang
Keyword(s):  
Preventive Maintenance ◽  
Hydraulic System ◽  
Maintenance Cost ◽  
Nsga Ii ◽  
Equipment Reliability ◽  
Equipment Availability ◽  
Age Regression ◽  
Working Age ◽  
The Difference ◽  
Crossover And Mutation

Based on the reliability analysis, this work presents a model of the preventive maintenance for the hydraulic system of platform firefighting vehicle, considering the working age regression factor and the equivalent service life. In this model, both the equipment availability and average maintenance cost are treated as the objective functions and constrained by the equipment reliability as well as the total working time. The non-dominated sorting genetic algorithm II (NSGA-II) algorithm is adopted to solve the previous optimization problem, wherein the constrained inequality functions in the stages of initialization, mutation, and crossover are introduced to assess the solution to meet the constraints or not, through the improvements in three aspects, namely, the improvement of the algorithm’s initialization to ensure the initial variables meet the equality constraint, the utilization of the mean division of the difference values to adjust the variables after the selection, and crossover and mutation of the gene. Numerical analysis is carried out to verify the feasibility of the improved algorithm, wherefrom the Pareto-optimal solutions for the preventive maintenance of the platform firefighting vehicle are obtained to provide the optimum strategy for the service engineers with different weighted factors.

scholarly journals The formation of the maintenance program and its impact on the increased level of power plants reliability

2020 ◽  
Vol 8 (4) ◽  
pp. 27-40
Author(s):  
Živoslav Adamović ◽  
Mladen Ivić ◽  
Veljko Vuković
Keyword(s):  
Preventive Maintenance ◽  
Power Plants ◽  
Technical System ◽  
Condition Based Maintenance ◽  
Maintenance Program ◽  
System Maintenance ◽  
Complex Technical System ◽  
Selection Of

The paper emphasizes the basic attitudes of complex technical system maintenance programming. Particularly it is performed an analysis and a selection of strategies for condition-based maintenance. The assessment of the established maintenance program varieties effectiveness was carried out by comparison with their basic indicators of effectiveness (for corrective and preventive maintenance).

Reliability analysis for electrical power systems based on importance measures

2019 ◽  
pp. 1748006X1989487
Author(s):  
Fangyu Liu ◽  
Hongyan Dui ◽  
Ziyue Li
Keyword(s):  
Power Systems ◽  
Power System ◽  
Reliability Analysis ◽  
Preventive Maintenance ◽  
System Performance ◽  
Electrical Power ◽  
Importance Measure ◽  
Reliability Engineering ◽  
Electrical Power System ◽  
Electrical Power Systems

With the introduction of reliability engineering, electrical power system reliability has become an important basis for decision-making in the power industry. Two operation cases of electrical power systems are considered in this article. When the system is in an ordinary way, the influence between two system components will affect the importance measure of one component. When some component is in maintenance, preventive maintenance for working components and corrective maintenance for failed components can be executed simultaneously to enhance electrical power system performance. In view of the above two cases, two importance measures are proposed to effectively guide the preventive maintenance, aiming to improve the system performance within a limited budget. Reliability analysis procedure and methods applied toward the two importance measures are then developed and illustrated with the analysis on a Dual Element Spot Network system with double power supplies and double loads. Finally, a strategy for preventive maintenance is proposed by ranking the importance of these components.

COMBINATORIAL POLYNOMIALLY COMPUTABLE CHARACTERISTICS OF SUBSTITUTIONS AND THEIR PROPERTIES

2020 ◽  
Vol 7 (2) ◽  
pp. 34-41
Author(s):  
VLADIMIR NIKONOV ◽  
◽  
ANTON ZOBOV ◽  
Keyword(s):  
Mathematical Expectation ◽  
Point Of View ◽  
Small Range ◽  
Computational Point ◽  
Wide Range ◽  
Bijective Function ◽  
The Difference ◽  
Element Base ◽  
Selection Of

The construction and selection of a suitable bijective function, that is, substitution, is now becoming an important applied task, particularly for building block encryption systems. Many articles have suggested using different approaches to determining the quality of substitution, but most of them are highly computationally complex. The solution of this problem will significantly expand the range of methods for constructing and analyzing scheme in information protection systems. The purpose of research is to find easily measurable characteristics of substitutions, allowing to evaluate their quality, and also measures of the proximity of a particular substitutions to a random one, or its distance from it. For this purpose, several characteristics were proposed in this work: difference and polynomial, and their mathematical expectation was found, as well as variance for the difference characteristic. This allows us to make a conclusion about its quality by comparing the result of calculating the characteristic for a particular substitution with the calculated mathematical expectation. From a computational point of view, the thesises of the article are of exceptional interest due to the simplicity of the algorithm for quantifying the quality of bijective function substitutions. By its nature, the operation of calculating the difference characteristic carries out a simple summation of integer terms in a fixed and small range. Such an operation, both in the modern and in the prospective element base, is embedded in the logic of a wide range of functional elements, especially when implementing computational actions in the optical range, or on other carriers related to the field of nanotechnology.

scholarly journals Age-dependency in mortality of Finnish family caregivers: a nationwide register-based study

2020 ◽  
Vol 30 (Supplement_5) ◽  
Author(s):  
T M Mikkola ◽  
H Kautiainen ◽  
M Mänty ◽  
M B von Bonsdorff ◽  
T Kröger ◽  
...  
Keyword(s):  
General Population ◽  
Family Caregivers ◽  
Family Caregiver ◽  
Causes Of Death ◽  
Lower Mortality ◽  
All Cause Mortality ◽  
The Difference ◽  
Caregiver Role ◽  
Selection Of

Abstract Purpose Mortality appears to be lower in family caregivers than in the general population. However, there is lack of knowledge whether the difference in mortality between family caregivers and the general population is dependent on age. The purpose of this study was to analyze all-cause mortality in relation to age in family caregivers and to study their cause-specific mortality using data from multiple Finnish national registers. Methods The data included all individuals, who received family caregiver's allowance in Finland in 2012 (n = 42 256, mean age 67 years, 71% women) and a control population matched for age, sex, and municipality of residence (n = 83 618). Information on dates and causes of death between 2012 and 2017 were obtained from the Finnish Causes of Death Register. Flexible parametric survival modeling and competing risk regression adjusted for socioeconomic status were used. Results The total follow-up time was 717 877 person-years. Family caregivers had lower all-cause mortality than the controls over the follow-up (8.1% vs. 11.6%) both among women (hazard ratio [HR]: 0.64, 95% CI: 0.61-0.68) and men (HR: 0.73, 95% CI: 0.70-0.77). Younger adult caregivers had equal or only slightly lower mortality than their controls, but after age 60, the difference increased markedly resulting in over 10% lower mortality in favor of the caregivers in the oldest age groups. Caregivers had lower mortality for all the causes of death studied, namely cardiovascular, cancer, neurological, external, respiratory, gastrointestinal and dementia than the controls. Of these, the lowest was the risk for dementia (subhazard ratio=0.29, 95%CI: 0.25-0.34). Conclusions Older family caregivers have lower mortality than the age-matched controls from the general population while younger caregivers have similar mortality to their peers. This age-dependent advantage in mortality is likely to reflect selection of healthier individuals into the family caregiver role. Key messages The difference in mortality between family caregivers and the age-matched general population varies considerably with age. Advantage in mortality observed in family caregiver studies is likely to reflect the selection of healthier individuals into the caregiver role, which underestimates the adverse effects of caregiving.

scholarly journals A microfluidic device enabling drug resistance analysis of leukemia cells via coupled dielectrophoretic detection and impedimetric counting

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yağmur Demircan Yalçın ◽  
Taylan Berkin Töral ◽  
Sertan Sukas ◽  
Ender Yıldırım ◽  
Özge Zorlu ◽  
...  
Keyword(s):  
Drug Resistance ◽  
K562 Cells ◽  
Leukemia Cells ◽  
Drug Resistant ◽  
Wild Type ◽  
Gene Expressions ◽  
Before And After ◽  
The Difference ◽  
Selection Of ◽  
Resistant Cells

AbstractWe report the development of a lab-on-a-chip system, that facilitates coupled dielectrophoretic detection (DEP-D) and impedimetric counting (IM-C), for investigating drug resistance in K562 and CCRF-CEM leukemia cells without (immuno) labeling. Two IM-C units were placed upstream and downstream of the DEP-D unit for enumeration, respectively, before and after the cells were treated in DEP-D unit, where the difference in cell count gave the total number of trapped cells based on their DEP characteristics. Conductivity of the running buffer was matched the conductivity of cytoplasm of wild type K562 and CCRF-CEM cells. Results showed that DEP responses of drug resistant and wild type K562 cells were statistically discriminative (at p = 0.05 level) at 200 mS/m buffer conductivity and at 8.6 MHz working frequency of DEP-D unit. For CCRF-CEM cells, conductivity and frequency values were 160 mS/m and 6.2 MHz, respectively. Our approach enabled discrimination of resistant cells in a group by setting up a threshold provided by the conductivity of running buffer. Subsequent selection of drug resistant cells can be applied to investigate variations in gene expressions and occurrence of mutations related to drug resistance.

scholarly journals Optimal Preventive Maintenance of Wind Turbine Components with Imperfect Continuous Condition Monitoring

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3801 ◽  
Author(s):  
Ahmed Raza ◽  
Vladimir Ulansky
Keyword(s):  
Wind Turbine ◽  
Condition Monitoring ◽  
Preventive Maintenance ◽  
False Negative ◽  
Maintenance Cost ◽  
Arbitrary Distribution ◽  
Average Lifetime ◽  
True Negative ◽  
Degradation Failure ◽  
Lifetime Maintenance

Among the different maintenance techniques applied to wind turbine (WT) components, online condition monitoring is probably the most promising technique. The maintenance models based on online condition monitoring have been examined in many studies. However, no study has considered preventive maintenance models with incorporated probabilities of correct and incorrect decisions made during continuous condition monitoring. This article presents a mathematical model of preventive maintenance, with imperfect continuous condition monitoring of the WT components. For the first time, the article introduces generalized expressions for calculating the interval probabilities of false positive, true positive, false negative, and true negative when continuously monitoring the condition of a WT component. Mathematical equations that allow for calculating the expected cost of maintenance per unit of time and the average lifetime maintenance cost are derived for an arbitrary distribution of time to degradation failure. A numerical example of WT blades maintenance illustrates that preventive maintenance with online condition monitoring reduces the average lifetime maintenance cost by 11.8 times, as compared to corrective maintenance, and by at least 4.2 and 2.6 times, compared with predetermined preventive maintenance for low and high crack initiation rates, respectively.

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