Maximum Repair Time Research Articles

Profit Comparison of Computer System with Hardware Redundancy Subject to Different Repair Activities

In this research paper, main concentrate of the authors on the profit comparison of computer system with hardware redundancy by introducing the concept of priority to software up-gradation, hardware preventive maintenance (PM) and hardware maximum repair time (MRT). The system fails independently from normal mode. All the repair activities such as hardware repair, software up-gradation, hardware preventive maintenance before failure and hardware replacement after maximum repair time are carried out by a single server immediately on need basis. All random variables are statistically independent. The negative exponential distribution is taken for the failure time of the component while the distributions of repair time, up-gradation time, preventive maintenance and replacement time are assumed arbitrary with different probability density functions. Semi-Markov process and regenerative point technique are used. The behaviour of profits of the system models have been examined for different parameters and costs.

Performance assessment of a newly developed non-invasive 2D beam profile monitor for high-intensity accelerators

In high-intensity accelerators, minimizing beam loss is paramount to avoid damages and activation of accelerator components. To achieve this, a reliable beam profile monitor is essential for assessing the beam center and spread. Additionally, the beam profile can be used to steer the beam during regular operation, thus reducing beam loss. In cases of irregular events, the monitor can initiate beam profile recording to identify and address any issues promptly. In this manuscript, we present a detailed description of a non-invasive 2D beam profile monitor, focusing on its components, operation, and most importantly, its reliability and failure modes. From operation experience, failure modes of the system and its effects were identified. Fault tree analysis was carried out. Failure rate of sheet generator was estimated using response surface method. Failure rates of components were used to estimate the failure rate of the system. From the target reliability, the required maximum repair time of the system was calculated.

A cost-benefit analysis for the appraisal of social and market prices in the probabilistic seismic risk assessment of building portfolios: A methodology for the evaluation of disaster risk reduction programs

A cost-benefit analysis can be a milestone for the probabilistic seismic risk assessment of building portfolios. This approach appraises social, economic, and technical aspects as evaluation criteria, becoming a reliable method for more accurate feasibility evaluation of Disaster Risk Reduction (DRR) programs. This paper proposes a simplified methodological approach to estimate the feasibility of intervention campaigns directed to seismic retrofitting for building portfolios. Its feature is the number of variables it encompasses such as: multiple intervention levels, resource distribution, maximum repair time, direct and indirect losses, simplified seismic resilience, number of casualties, amount of replacement buildings, and expected service life. Then, all these factors are analyzed using a conventional probabilistic seismic risk assessment, followed by the estimation of net cash flows in terms of social and market prices. The final profitability and feasibility are determined based on investment indicators (Net Present Value, Internal Rate of Return, and Cost-Benefit ratio). In addition, plots of maximum repair time and simplified seismic resilience (as a function of the resource distribution) are proposed as novel decision-making tools. To illustrate the methodology, a case study of six building portfolios grouped into two categories is presented. The portfolios are conformed by a Peruvian school typology designated as 780-PRE, typically two-story high with reinforced concrete moment-resisting frames plus infill-walls and confined masonry walls. The demonstrative case included eleven target scenarios to assess the as-built and several intervention conditions, based on incremental seismic retrofitting measures. Results confirm that social prices influence the decision-making process, even making feasible projects that were initially unfeasible (when solely appraised under market prices). Finally, the authors propose further applications of this methodology as a tool to support the development of reliable DRR-programs.

IoT platform for failure management in water transmission systems

In aging water supply systems, many components have exceeded their service life. Consequently, tools are needed to efficiently manage the failures in these systems. This work describes the development and implementation of a web tool for the management of breakdowns in water transmission networks. The proposed tool, called wAIter, consists of a network of wireless water pressure sensors that send real-time data to an IoT platform. The core of the platform consists of a rule-based decision algorithm, which detects and classifies failures based on the recorded pressure values and then sends an alert to repair them. In addition, wAIter uses the mathematical model of the hydraulic network to estimate the maximum repair time without causing supply interruptions. This information is key in the decision-making process to repair breakdowns and facilitate repair work management. Finally, the results of the implementation in a real water transmission network are presented.

STOCHASTIC MODELING AND SENSITIVITY ANALYSIS OF AN INTEGRATED HARDWARE-SOFTWARE SYSTEM SUBJECT TO DIFFERENT WEATHER CONDITIONS

The current study covenants with stochastic investigation of an integrated hardware-software system considering hardware failure, software up-gradation upon failure, precautionary maintenance (PM) after a pre-determined process time, maximum repair time of hardware and different weather conditions. All time dependent indiscriminate variables are arbitrarily dispersed. Some important reliability measures like MTSF, availability and revenue of the system are obtained by using well established techniques semi-Markov process. Regenerative point technique has also been taken into consideration during model development. Sensitivity analysis of these measures is also performed. Finally, empirical analysis is done to demonstrate the results for a specific case. To climax the significance of the study, graphs of MTSF, availability, profit and sensitivity are also depicted.

Data-driven predictive maintenance policy based on multi-objective optimization approaches for the component repairing problem

In systems with many components that are required to be constantly active, such as refineries, predicting the components that will break in a time interval after a stoppage may significantly increase their reliability. However, predicting the set of components to be repaired is a challenging task, especially when several conditions (e.g. breakage probability, repair time and cost) have to be considered simultaneously. A data-driven predictive maintenance policy is proposed for maximizing the system reliability and minimizing the maximum repair time, considering both budget and human resources constraints. Therefore, a data-driven algorithm is designed for extracting component breakage probabilities. Then, two bi-objective optimization approaches are proposed for determining the set of components to repair. The former is based on the formulation of a bi-objective mixed integer linear programming model solved through the AUGMEnted ε-CONstraint (AUGMECON) method. The latter implements a bi-objective large neighbourhood search, outperforming the first approach.

Stochastic behavior of parallel system with expert repair and maintenance

This paper examines the effect of preventive maintenance and repair done by different repairpersons on the system performance. By means of semi-Markov process and regenerative point technique, the researcher has developed a stochastic model of two unit parallel system. Both units are identical in nature. A usual repairperson visits the system to conduct preventive maintenance at the completion of maximum operation time and repair at the failure stage of the unit. At the elapse of the pre-definite time (called maximum repair time), the usual repairperson inspects the failed unit to examine the feasibility of further repair by the expert repairperson; otherwise that unit will be replaced by a new one with some replacement time. The unit may work as good as new after getting maintenance, repair and replacement as well. The switch devices are considered as perfect. Various measures of system usefulness such as MTSF, availability and profit have been derived to depict the usefulness of expert repair facility.

Profit analysis of a computer system with preventive maintenance and priority subject to maximum operation and repair times

The aim of the present study is to carry out the profit analysis of a computer system by considering the concept of priority to preventive maintenance over different hardware and software repair activities. For this purpose, three stochastic models have been developed under different priority policies. A single repair facility is available to perform all repair activities. The hardware unit undergoes replacement after a pre-specific maximum repair time. The repairman performs the preventive maintenance of the whole system after a pre-fixed maximum operation time. All time-dependent failure rates follow exponential distribution, while the repair rates follow arbitrary distribution. Switch devices, repairs and preventive maintenance are perfect. All random variables are statistically independent. Semi-Markov process and regenerative point technique were used to derive the necessary system effectiveness measure to evaluate the profit function of all the three models. To highlight the importance of the study, graphs for profit difference between models have been depicted for a particular set of values of various parameters with respect to preventive maintenance.

Stochastic Analysis of a Two Unit Parallel System with Maximum Repair and Order Time for the New Unit

Stochastic Analysis of a Two Unit Parallel System with Maximum Repair and Order Time for the New Unit

Optimal replacement policy based on maximum repair time for a random shock and wear model

We study a \(\delta \) shock and wear model in which the system can fail due to the frequency of the shocks caused by external conditions, or aging and accumulated wear caused by intrinsic factors. The external shocks occur according to a Bernoulli process, i.e., the inter-arrival times between two consecutive shocks follow a geometric distribution. Once the system fails, it can be repaired immediately. If the system is not repairable in a pre-specific time D, it can be replaced by a new one to avoid the unnecessary expanses on repair. On the other hand, the system can also be replaced whenever its number of repairs exceeds N. Given that infinite operating and repair times are not commonly encountered in practical situations, both of these two random variables are supposed to obey general discrete distribution with finite support. Replacing the finite support renewal distributions with appropriate phase-type (PH) distributions and using the closure property associated with PH distribution, we formulate the maximum repair time replacement policy and obtain analytically the long-run average cost rate. Meanwhile, the optimal replacement policy is also numerically determined by implementing a two-dimensional-search process.

Stochastic Analysis of a Redundant System with Maximum Repair Time and Priority for Operation over Preventive Maintenance

The main goal of the present study is to analyze a redundant system by using the concept of priority to operation over Preventive Maintenance (PM) and Maximum Repair Time (MRT). For this purpose, two stochastic models are developed. The concept of MRTis studied in the second model in addition to the assumptions of first model. There is a single server who visits the system immediately as and when required. The server takes the unit under preventive maintenance after a maximum operation time at normal mode if one standby unit is available for operation. If the repair of the failed unit is not possible up to an MRT, failed unit is replaced by new one. The failure time, maximum operation time and MRT distributions of the unit are considered as exponentially distributed while repair and maintenance time distributions are considered as arbitrary. Various measures of system effectiveness are obtained by using the technique of semi-Markov process and RPT. To compare the performance of stochastic models graphs for several reliability measures are drawn.

Reliability modelling of a parallel system with maximum operation and repair times

A parallel system of two identical units has been analysed under the aspects of maximum operation and repair times. The unit fails directly from normal mode. A single server is called immediately to conduct preventive maintenance of the unit after a pre-specific time 't' (called maximum operation time). The replacement of the unit is made by new one in case its repair is not possible by the server in a given maximum repair time. The unit works as new after preventive maintenance and repair. The distributions of failure time of the unit, the time to which unit undergoes for preventive maintenance and replacement are taken as negative exponential. However, the distributions of preventive maintenance, repair and replacement times are considered as arbitrary with different probability density functions. The expressions for several reliability measures are derived in steady-state using semi-Markov process and regenerative point technique. The graphical behaviour of the MTSF, availability and profit function has been examined giving arbitrary values to various parameters and costs. The profit of the system model has also been obtained considering different costs.

Cost Analysis of a Two-Unit Cold Standby System Considering Hardware, Software Failures and Inspection with Maximum Repair Time

The present paper deals with a reliability model of a two unit cold standby system that exposed to two types of failures. In each unit there are hardware and software componentes work together and fail independently. there is a single server who visits the system immediately when required. The server inspects the unit in case of software failure and decides either to repair or replace it. The h/w components undergo for repair at their failure and are replaced by new one in case of arriving to maximum repair time. All time distributions are considered to be exponential. Various measures of reliability of the system are obtained using regenerative point technique. Finally simulation study is done to illustrate the results.

Stochastic behavior of a cold standby system with maximum repair time

Article history: Received January 29, 2015 Received in revised format: April 28, 2015 Accepted May 7, 2015 Available online May 8 2015 The main aim of the present paper is to analyze the stochastic behavior of a cold standby system with concept of preventive maintenance, priority and maximum repair time. For this purpose, a stochastic model is developed in which initially one unit is operative and other is kept as cold standby. There is a single server who visits the system immediately as and when required. The server takes the unit under preventive maintenance after a maximum operation time at normal mode if one standby unit is available for operation. If the repair of the failed unit is not possible up to a maximum repair time, failed unit is replaced by new one. The failure time, maximum operation time and maximum repair time distributions of the unit are considered as exponentially distributed while repair and maintenance time distributions are considered as arbitrary. All random variables are statistically independent and repairs are perfect. Various measures of system effectiveness are obtained by using the technique of semi-Markov process and RPT. To highlight the importance of the study numerical results are also obtained for MTSF, availability and profit function. Growing Science Ltd. All rights reserved. 5 © 201

Reliability measures of a computer system with priority to PM over the H/W repair activities subject to MOT and MRT

Article history: Received September 18, 2014 Accepted 15 December 2014 Available online December 16 2014 This paper concentrates on the evaluation of reliability measures of a computer system of twoidentical units having independent failure of h/w and s/w components. Initially one unit is operative and the other is kept as spare in cold standby. There is a single server visiting the system immediately whenever needed. The server conducts preventive maintenance of the unit after a maximum operation time. If server is unable to repair the h/w components in maximum repair time, then components in the unit are replaced immediately by new one. However, only replacement of the s/w components has been made at their failure. The priority is given to the preventive maintenance over repair activities of the h/w. The time to failure of the components follows negative exponential distribution whereas the distribution of preventive maintenance, repair and replacement time are taken as arbitrary. The expressions for some important reliability measures of system effectiveness have been derived using semi-Markov process and regenerative point technique. The graphical behavior of the results has also been shown for a particular case. Growing Science Ltd. All rights reserved. 5 © 201

A single unit system with preventive maintenance and repair subject to maximum operation and repair times

The purpose of the present study is to determine reliability measures of a single-unit system considering arbitrary distributions for the random variables associated with failure time, preventive maintenance and repair times, maximum operation time, maximum repair time and replacement time. The system fails completely either directly from normal mode or via partial failure. There is a single server who visits the system immediately to do repair activities. The partially failed operating unit is shutdown after pre-specific time (called maximum operation time) for preventive maintenance. However, repair of the unit is done after its complete failure. The completely failed unit is replaced by new one if server is unable to do its repair within a maximum repair time. The unit works as new after preventive maintenance and repair. The expressions for some important measures of system effectiveness are derived using semi-Markov process and regenerative point technique. The numerical results for a particular case are obtained to depict the behavior of MTSF, availability and profit function with respect to maximum operation time for fixed values of other parameters and costs.

Reliability Measure of a Standby System with Arrival Time of the Server Subject to Maximum Operation and Repair Time

Reliability Measure of a Standby System with Arrival Time of the Server Subject to Maximum Operation and Repair Time

Cost-Benefit Analysis of a Computer System with Priority to Preventive Maintenance over Hardware Repair Subject to Maximum Operation and Repair Times

A computer system is analyzed considering the concept of priority to Preventive Maintenance (PM) over hardware repair subject to maximum operation and repair times. Two-identical units of the computer system have been taken up-one is initially operative and other is kept as spare in cold standby. In each unit, hardware (h/w) and software (s/w) work together and may fail independently from normal mode. There is a single server who visits the system immediately when needed to carry out repair activities. PM of the unit is conducted after a Maximum Operation Time (MOT). If repair of the h/w is not possible up to a maximum repair time, it is replaced by a new one with some replacement time. However, only replacement of the s/w is made giving some replacement time with the new one when s/w fails to execute the program properly. Priority to PM of the unit is given over h/w repair. The failure time of the unit follows negative exponential distribution while the distributions of PM, repair and replacements are taken as arbitrary. To carry out the cost-benefit analysis, expressions for several reliability measures are obtained by using semi-Markov and regenerative point technique. The graphical behaviour of some important performance measures of the system has been examined giving particular values to various parameters and costs.

Reliability modeling of a computer system with preventive maintenance and priority subject to maximum operation and repair times

The main focus of this paper is on the reliability modelling of a computer system considering the concepts of redundancy, preventive maintenance and priority in repair activities. Two identical units of a computer system are taken—one unit is initially operative and the other is kept as spare in cold standby. In each unit h/w and s/w work together and may fail independently from normal mode. There is a single server who visits the system immediately as and when needed. Server conducts preventive maintenance of the unit (computer system) after a maximum operation time. Repair of the h/w is done at its failure while s/w is upgraded from time to time as per requirements. If server unable to repair the h/w in a pre-specific time (called maximum repair time), h/w is replaced by new one giving some replacement time. Priority to h/w repair is given over s/w up gradation if, in one unit s/w is under up-gradation and h/w fails in another operative unit. The failure time of h/w and s/w follows negative exponential distributions while the distributions of preventive maintenance, h/w repair/replacement and s/w up-gradation times are taken as arbitrary with different probability density functions. The expressions for several reliability and economic measures are derived in steady state using semi-Markov process and regenerative point technique. The graphical study of mean time to system failure (MTSF) and profit function has also been made giving particular values to various parameters and costs.

Stochastic Modeling of a Computer System with Priority to PM over S/W Replacement Subject to Maximum Operation and Repair Times

ABSTRACT This paper focuses on the stochastic modeling of a computer system of two identical units- one is initially operative and other is kept as spare in cold standby. In each unit h/w and s/w components work together and fail independently. There is a single server who visits the system immediately as and when required. The server takes the unit under preventive maintenance after a maximum operation time at normal mode. The h/w components under go for repair at their failure and are replaced by new one in case these are not repaired up to a maximum repair time. However, s/w components are replaced by new one instead of repair. Priority is given to the preventive maintenance (PM) of the unit over replacement of the s/w components. The failure time distribution of the components follow negative exponential whereas the distributions of preventive maintenance, repair and replacement time are taken as arbitrary with different probability density functions. Several reliability and economic indices have been obtained using semi-Markov and regenerative point technique. The graphical study of the results has also been made.