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The purpose of this paper is to develop a stochastic detailed schedule for a preventive/scheduled/periodic maintenance program of a military aircraft, specifically a rotorcraft or helicopter.

The new model, entitled the military “periodic aviation maintenance stochastic schedule” (PAM-SS), develops a stochastic detailed schedule for a PUMA SA 330SM helicopter for the 50-h periodic inspection, using cyclic operation network (CYCLONE) and Monte Carlo simulation (MCS) techniques. The PAM-SS model identifies the different periodic inspection tasks of the maintenance schedule, allocates the resources required for each task, evaluates a stochastic duration of each inspection task, evaluates the probability of occurrence for each breakdown or repair, develops the CYCLONE model of the stochastic schedule and simulates the model using MCS.

The 50-h maintenance stochastic duration follows a normal probability distribution and has a mean value of 323 min and a standard deviation of 23.7 min. Also, the stochastic maintenance schedule lies between 299 and 306 min for a 99 per cent confidence level. Furthermore, except the pilot and the electrical team (approximately 90 per cent idle), all other teams are around 40 per cent idle. A sensitivity analysis is also performed and yielded that the PAM-SS model is not sensitive to the number of technicians in each team; however, it is highly sensitive to the probability of occurrence of the breakdowns/repairs.

The PAM-SS model is specifically developed for military rotorcrafts, to manage the different resources involved in the detailed planning and scheduling of the periodic/scheduled maintenance, mainly the 50-h inspection. It evaluates the resources utilization (idleness and queue), the stochastic maintenance duration and identifies backlogs and bottlenecks.

The PAM-SS tackles military aircraft planning and scheduling in a stochastic methodology, considering uncertainties in all inspection task durations and breakdown or repair durations. The PAM-SS, although developed for rotorcrafts can be further developed for any other type of military aircraft or any other scheduled maintenance program interval.

Future‐time is of concern – and of increasing concern – with police system. The modern police has existed in Nigeria for about 69 years (1930‐1999). These comments are an attempt to predict the future of the Nigerian police. Using the events of more than six decades in Nigeria as a baseline, intelligible guesses are made about what to expect of the general shape and character of the Nigerian police in 20 years from now – the year 2043. Prognostication of the future with respect to the Nigerian police is made in two broad areas: areas of continuities in policing; and areas of changes that might or might not occur in the police. And awareness of the continuities in policing in Nigeria provides perspective for predicting changes that might occur in the Nigeria police in the future. The essay is aimed at enabling the Nigerian police to anticipate and keep pace with changes so that it can minimize its own problems, enhance its functional performance and fulfil its proper role in society.

This paper aims to present approaches towards improving some specific infrastructure maintenance principles, strategies, models and practices, based on a recent study of bridge management systems in Hong Kong. A specific goal is to develop better informed and more systematic approaches to condition assessment, deterioration forecasting, and maintenance decision making over the life‐cycle of the built asset.

Improved performance prediction and decision‐making approaches are developed and presented based on a research exercise to formulate a maintenance management framework for concrete bridge elements in Hong Kong. This includes for example, the presentation of decision‐making approaches for optimizing inspection intervals on bridge expansion joints.

The findings show that judicious integration is needed in incorporating valuable elements of, and lessons learned from, previous practice with proposed new strategies/ principles, models and practices for specific scenarios.

Based on the findings, practitioners' understandings can be deepened as regards the barriers to improving condition assessment, deterioration forecasting, and maintenance decision making over the life‐cycle of the built asset. Furthermore, the results also provide useful information for developing strategies and practices to improve currently used infrastructure management systems.

Major obstacles are overcome in developing better informed and more systematic approaches as above, and in extending current knowledge on condition assessment, performance prediction and decision‐making models by utilizing more pertinent data and addressing some barriers in practical implementation.

The aim of this research paper is to generalize the previous works on the design of accelerated life tests (ALTs) for periodic inspection and Type I censoring and to promote the use of an exponentiated Weibull (EW) distribution in accelerated life testing.

Statistically optimal ALT plans are suggested for items whose lifetime follows the EW distribution under periodic inspection and Type I censoring. It is assumed that the mean lifetime (scale parameter) is a log‐linear function of stress and that the shape parameters are independent of stress. Given shape parameters, design stress and high test stress, the test plan is optimized with respect to the low test stress and the proportion of test units are also allocated to this test stress. The asymptotic variance (AsVar) of the maximum likelihood estimator of log mean life at the design stress is used as an optimality criterion with equally spaced inspection times. A FORTRAN program was written to calculate the optimal plans. Procedures for planning of an ALT, including selection of sample size, have also been discussed. An illustration of the optimal ALT plans has been done through a numerical example.

Computational findings for various values of the shape parameters indicate that the AsVar of log mean life at the design stress is insensitive to the number of inspection times and to misspecifications of imputed failure probabilities at design and high test stresses. Computational findings also show that optimal designs of ALT previously obtained for exponential, Rayleigh, and Weibull distributions become special cases of the EW distribution. Thus, the EW distribution is a useful and widely applicable reliability model for optimal ALT plans.

The present investigation features the EW distribution of lifetimes of test items and it generalizes the previous works on accelerated life testing. Furthermore, the propose test plans can be applied to estimate the lifetime of highly reliable product or material, if a researcher designs a test under the assumption of this model.

This paper proposes a heuristic, data-driven approach to the rapid performance evaluation of periodic maintenance on complex production plants. Through grouping, maintenance interval (MI)-based evaluation and performance assessment, potential nonvalue-adding maintenance elements can be identified in the current maintenance structure. The framework reduces management complexity and supports the decision-making process for further maintenance improvement.

The evaluation framework follows a prescriptive research approach. The framework is structured in three steps, which are further illustrated in the case study. The case study utilizes real-life data to verify the feasibility and effectiveness of the proposed framework.

Through a case study conducted on 9,538 pieces of equipment from eight offshore oil and gas production platforms, the results show considerable potential for maintenance performance improvement, including up to a 23% reduction in periodic maintenance hours.

The problem of performance evaluation under limited data availability has barely been addressed in the literature on the plant level. The proposed framework aims to provide a quantitative approach to reducing the structural complexity of the periodic maintenance evaluation process and can help maintenance professionals prioritize the focus on maintenance improvement among current strategies.

The proposed framework is especially suitable for initial performance assessment in systems with a complex structure, limited maintenance records and imperfect data, as it reduces management complexity and supports the decision-making process for further maintenance improvement. A similar application has not been identified in the literature.

The system encountering dormant failure subject to sequential inspections is modeled and the emphasis is made on determining the availability and long-run average cost rate for the model. The derived results are then utilized to obtain the optimal inspection period minimizing the cost.

Explicitly, a system with a functional and a failed state is taken into account. Inspections are performed to reveal the dormant failures and are assumed to be carried out at time T, T + aT, T + aT+a² T, … where 0 < a = 1 in each cycle. Perfect repairs taking random times are performed if the system is found in a failed state during any inspection.

Some theorems on the point availability, limiting availability and long-run average cost rate are obtained in the study. An illustration is shown to explain the results obtained in the proposed work. The effect of inspection time on the availability and cost rate is also analyzed graphically.

The availability and cost rate for a system with dormant failure under a sequential inspection policy are figured out unlike previous research.

All built facility begins to show signs of deterioration immediately after the facility is completed and put to use, thus necessitating routine maintenance. Increase in defects due to age, usage, and other factors, requires extensive maintenance activities known as renovation. The data used for a typical renovation plan can be collected using the condition assessment (CA) tool which depends on physical inspection of the defects or through a facility condition index which hinges on harnessing and analyzing the information in the operational history of the facility. The purpose of this paper is to examine the quality of a typical renovation plan using both tools.

The single case study of qualitative research was adopted. The data were collected through the principle of semi-structured questionnaire complemented with interviews and document analysis. The documents include periodic operational reports and a CA report used for planned renovation exercise of the Facilities Management (FM) Unit in a higher education institution in South Africa.

The findings revealed that although the FM Unit produces periodic reports, but there was no evidence of detailed analysis of the reports. Therefore, the programmed renovation exercises are based purely on the information from a CA.

This research is a single site case study of qualitative research; the data collected are limited and not sufficient for generalization of the results. Furthermore, the lack of record of the analysis of the operational history in the periodic reports negatively affected the computation of facilities condition index (FCI). Thus it was not possible to demonstrate the strength of FCI over CA from empirical information.

The quality of a typical renovation plan is influenced by the tool used for data collection. Although the CA tool is commonly used, experience shows that the renovation exercise developed from such records is prone to many execution setbacks, such as frequent scope changes and the associated cost and time overruns. These setbacks can be minimized if the FCI is used as the tool for data collection.

The purpose of this paper is to determine optimal replacement threshold and optimal inspection interval for an item subjected to condition-based maintenance (CBM). The primarily assumption is that the item's failure replacement cost depends on the item's degradation state at which failure occurs and/or the time the item fails. The cost of inspection is also taken into account.

The control limit replacement policy framework, already reported by some research referred to in this paper, is first extended to include the non-decreasing failure replacement cost assumption. Then, for alternative inspection intervals, replacement thresholds together with their associated total cost including the inspection cost are computed. By comparing the total costs, the optimal inspection interval and its corresponding optimal replacement threshold are simultaneously identified.

The mathematical formulation required for the determination of optimal replacement threshold and optimal inspection interval for an item subjected to CBM under the assumption of non-decreasing failure cost is provided.

In some practical situations where CBM is implemented, the failure replacement cost may depend on the time the failure happens and/or may depend on the system's degradation state. In addition, inspections often incur cost. Under such circumstances, findings of this paper can be utilized for the determination of optimal replacement threshold and optimal inspection interval for the underlying system.

Using the approach proposed in this paper, one could obtain the optimal replacement threshold and the optimal inspection interval for a system subjected to CBM.

The present study proposes two types of periodical inspection policies for a scale which weighs products in the final stage of manufacturing some specific products, such as chemical products. The scale is inspected at time iT(i=1,2, … ). Under ModelI, an inspection operation involves detection of a scale malfunction or inaccuracy as well as an adjustment activity. Under ModelII, an inspection is conducted only to detect a scale malfunction. If a scale malfunction is detected, an adjustment activity follows. For each model, the fraction defective and the long‐run average cost are formulated. We then examine the existence of an inspection interval T_α which makes the fraction defective under a prespecified value α (0< α <1). An economical inspection interval T^* minimizing the long‐run average cost is also discussed.