scholarly journals Optimizing a Multi-State Cold-Standby System with Multiple Vacations in the Repair and Loss of Units

Mathematics ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 913
Author(s):  
Juan Eloy Ruiz-Castro
Keyword(s):  
Preventive Maintenance ◽  
External Shocks ◽  
Matrix Analytic Methods ◽  
Multiple Vacation ◽  
Phase Type ◽  
Arrival Processes ◽  
Repair Facility ◽  
The Times ◽  
Set Up ◽  
Algorithmic Form

A complex multi-state redundant system with preventive maintenance subject to multiple events is considered. The online unit can undergo several types of failure: both internal and those provoked by external shocks. Multiple degradation levels are assumed as both internal and external. Degradation levels are observed by random inspections and, if they are major, the unit goes to a repair facility where preventive maintenance is carried out. This repair facility is composed of a single repairperson governed by a multiple vacation policy. This policy is set up according to the operational number of units. Two types of task can be performed by the repairperson, corrective repair and preventive maintenance. The times embedded in the system are phase type distributed and the model is built by using Markovian Arrival Processes with marked arrivals. Multiple performance measures besides the transient and stationary distribution are worked out through matrix-analytic methods. This methodology enables us to express the main results and the global development in a matrix-algorithmic form. To optimize the model, costs and rewards are included. A numerical example shows the versatility of the model.

scholarly journals A k-out-of-n reliability system with an unreliable server and phase type repairs and services: the (N,T) policy

2001 ◽  
Vol 14 (4) ◽  
pp. 361-380 ◽  
Author(s):  
Srinivas R. Chakravarthy ◽  
A. Krishnamoorthy ◽  
P. V. Ushakumari
Keyword(s):  
Performance Measures ◽  
Matrix Analytic Methods ◽  
Steady State Analysis ◽  
Numerical Examples ◽  
Unreliable Server ◽  
Failure Times ◽  
Vacation Time ◽  
Phase Type ◽  
Repair Facility ◽  
Random Amount

In this paper we study a k-out-of-n reliability system in which a single unreliable server maintains n identical components. The reliability system is studied under the (N,T) policy. An idle server takes a vacation for a random amount of time T and then attends to any failed component waiting in line upon completion of the vacation. The vacationing server is recalled instantaneously upon the failure of the Nth component. The failure times of the components are assumed to follow an exponential distribution. The server is subject to failure with failure times exponentially distributed. Repair times of the component, fixing times of the server, and vacationing times of the server are assumed to be of phase type. Using matrix-analytic methods we perform steady state analysis of this model. Time spent by a failed component in service, total time in the repair facility, vacation time of the server, non-vacation time of the server, and time until failure of the system are all shown to be of phase type. Several performance measures are evaluated. Illustrative numerical examples are presented.

scholarly journals Preliminary Investigation on Systems for the Preventive Diagnosis of Faults on Agricultural Operating Machines

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1547
Author(s):  
Massimo Cecchini ◽  
Francesca Piccioni ◽  
Serena Ferri ◽  
Gianluca Coltrinari ◽  
Leonardo Bianchini ◽  
...  
Keyword(s):  
Preventive Maintenance ◽  
Continuous Monitoring ◽  
Preliminary Investigation ◽  
Agricultural Machinery ◽  
Technical Literature ◽  
Maintenance System ◽  
The People ◽  
Bearing Failures ◽  
The Times ◽  
Set Up

This paper aims to investigate failures induced by vibrations on machines, focusing on agricultural ones. The research on literature has brought to light a considerable amount of data on the driven vehicles and not much on the operating machines, including the ones that we looked for. For this reason, it was decided to direct a survey with the people who work with agricultural machinery every day: operators, sub-contractors, and producers. They were asked about the most frequent breakage, particularly in relation to the rotary harrow, the topic of this work. The questionnaire results showed the types of failures the harrow is most vulnerable to, indicating the times of failure and reparation and the need to set up a potentially useful preventive maintenance supporting system on these machines. Part of the work was then focused on the proposition of a method to investigate bearing failures in the rotary harrow, considering that these have been analyzed in the technical literature and in the survey as the most at-risk components. The proposed method in this work serves as a beginning for the development of a future on board sent-shore-based maintenance system for continuous monitoring of the bearing.

Analysis of R-out-of-N repairable systems: the case of phase-type distributions

2004 ◽  
Vol 36 (1) ◽  
pp. 116-138 ◽  
Author(s):  
Yonit Barron ◽  
Esther Frostig ◽  
Benny Levikson
Keyword(s):  
Repairable System ◽  
Repairable Systems ◽  
Regenerative Processes ◽  
Numerical Examples ◽  
Independent Components ◽  
Duality Results ◽  
Phase Type ◽  
Phase Type Distributions ◽  
Two Systems ◽  
Repair Facility

An R-out-of-N repairable system, consisting of N independent components, is operating if at least R components are functioning. The system fails whenever the number of good components decreases from R to R-1. A failed component is sent to a repair facility. After a failed component has been repaired it is as good as new. Formulae for the availability of the system using Markov renewal and semi-regenerative processes are derived. We assume that either the repair times of the components are generally distributed and the components' lifetimes are phase-type distributed or vice versa. Some duality results between the two systems are obtained. Numerical examples are given for several distributions of lifetimes and of repair times.

FFT Analysis Using LabView as a Part of Vibration and Preventive Maintenance Class for Senior Level MET students

2005 ◽  
Author(s):  
Aniruddha Mitra ◽  
Sahana Sen
Keyword(s):  
Preventive Maintenance ◽  
Laboratory Experiments ◽  
Vibration Signal ◽  
Engineering Technology ◽  
Technology Program ◽  
Student Activities ◽  
Labview Software ◽  
Vibration Data ◽  
Set Up ◽  
Fft Analysis

An existing senior level elective course on vibration in Mechanical Engineering Technology program at Georgia Southern University has been modified significantly. Two major components have been added to this course. Those are theoretical topics on preventive maintenance and laboratory experiments. As a part of laboratory experiments, Fast Fourier Transform (FFT) was introduced as a possible tool for vibration analysis for the purposes of machine diagnosis. Utilizing the current laboratory set up for the data acquisition systems, LabView software has been used for FFT analysis of signals from various sources. Four different modules were developed and implemented. The modules are as follows: random variation in acceleration of a toy cart due to roughness of the track and pulley, regular uniform wave signal which is generated by the lateral vibration of a cantilever beam at its natural frequency, signal generated by the imported raw data from other sources (e.g. MATLAB) and vibration signal of a shaft mounted on ball bearings in order to detect the defects in the bearing. Each of these modules is illustrated in this paper with suitable examples and suggested student activities and involvements. The results from FFT analysis have been cross checked using other methods and observations. As a follow up, students have been taken to a local industry where significant amount of emphasis is given to preventive maintenance of machineries by vibration data analysis using FFT. Future possible projects include the analysis of vibration data gathered from actual machine shop. This project opens the scope for greater collaborative effort between local industries and classroom activities.

scholarly journals Volume and duration of losses in finite buffer fluid queues

2015 ◽  
Vol 52 (3) ◽  
pp. 826-840 ◽  
Author(s):  
Fabrice Guillemin ◽  
Bruno Sericola
Keyword(s):  
Busy Period ◽  
Buffer Capacity ◽  
Exact Expression ◽  
Loss Probability ◽  
Finite Buffer ◽  
Fluid Queues ◽  
Buffer Content ◽  
Phase Type ◽  
Phase Type Distributions ◽  
Arrival Processes

We study congestion periods in a finite fluid buffer when the net input rate depends upon a recurrent Markov process; congestion occurs when the buffer content is equal to the buffer capacity. Similarly to O'Reilly and Palmowski (2013), we consider the duration of congestion periods as well as the associated volume of lost information. While these quantities are characterized by their Laplace transforms in that paper, we presently derive their distributions in a typical stationary busy period of the buffer. Our goal is to compute the exact expression of the loss probability in the system, which is usually approximated by the probability that the occupancy of the infinite buffer is greater than the buffer capacity under consideration. Moreover, by using general results of the theory of Markovian arrival processes, we show that the duration of congestion and the volume of lost information have phase-type distributions.

scholarly journals Innovation and Entrepreneurship Education and Teaching Based on “Internet+” Research and Exploratio

2019 ◽  
Vol 3 (2) ◽  
pp. 113
Author(s):  
Hongyan Pei
Keyword(s):  
Education Reform ◽  
Entrepreneurship Education ◽  
Social Background ◽  
Colleges And Universities ◽  
The State ◽  
Educational Goals ◽  
State Council ◽  
The Times ◽  
Set Up ◽  
Innovation And Entrepreneurship

<p>In order to promote mass entrepreneurship and innovation, the General Office of the State Council issued the implementation opinions on deepening innovation and entrepreneurship education reform in institutions of higher learning. According to the guidelines for innovation and entrepreneurship proposed by the State Council, colleges and universities should combine the entrepreneurial needs of students and the innovative needs of the society, set up educational goals around the orientation of running a school, and carry out educational reform activities with innovation and entrepreneurship as the theme. Based on the overall social background of "Interne+" and distinct characteristics of the times, this paper analyzes the problems existing in innovation and entrepreneurship education in colleges and universities, and explores effective strategies for implementing innovation and entrepreneurship education in colleges and universities.</p>

Improving Teachers' Digital Competence to Bridge the Language Gap

2020 ◽  
pp. 67-82
Author(s):  
Manuela Caravello ◽  
Cristina A. Huertas-Abril ◽  
María Elena Gómez-Parra
Keyword(s):  
Flipped Classroom ◽  
Language Teachers ◽  
Basic Knowledge ◽  
Digital Competence ◽  
Foreign Language Teachers ◽  
Digital Innovation ◽  
Knowledge And Skills ◽  
Digital Skills ◽  
The Times ◽  
Set Up

This chapter aims to examine the digital skills that foreign language teachers must have in our global interconnected society and the ways in which they can acquire them. Pedagogical and digital innovation has been traveling along the same lines for some time. In recent years, however, in all fields of education—and more specifically in the didactic of foreign languages—several methods and techniques that increase the use of digital technology have been developed. Consequently, all teachers must keep up with the times. In this light, the objective of this chapter is to reflect on the pedagogical scenario that the digital age has set up, as well as on the ideal portrait that teachers must have. Then, the authors will focus on the specific digital skills that teachers who want to “flip” their teaching process should have: What are the basic knowledge and skills that a teacher must master if they wish to rethink their practices and embark on a flipped classroom approach?

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