scholarly journals Stochastic Analysis of a Three-Unit Non-Identical Repairable System with Simultaneous Working of Cold Standby Units

2021 ◽  
Author(s):  
S. Kadyan ◽  
Suresh Chander Malik ◽  
Gitanjali
Keyword(s):  
Power Supply ◽  
Stochastic Analysis ◽  
Transition Probabilities ◽  
Repairable System ◽  
Single Server ◽  
Solar Panels ◽  
Reliability Measures ◽  
Expected Number ◽  
Cold Standby ◽  
Regenerative Point Technique

Here, stochastic analysis of a repairable system of three units has been carried out by taking one unit in operation (called main unit) and two identical units (called duplicate units) in cold standby. The switch device is used to convert the standby units into operative mode. A single server is hired to handle repair activities of the units who visits the system instantly whenever needed. The repair done by the server is perfect and thus the repaired unit follows the same lifetime distribution as the original. The constant failure rates are considered for both main and the duplicate units while their repair time distributions are taken as arbitrary. Some important reliability measures including mean sojourn times (MST), transition probabilities (TP), mean time to system failure (MTSF), availability, expected number of repairs for both kinds of units separately, expected number of visits by the server and busy period analysis of the server due to repair are determined using semi-Markov process (SMP) and regenerative point technique (RPT). The arbitrary values of the parameters are considered to examine the behaviour of some significant reliability measures through graphs. The possible application of the system model can be visualized in a power supply system of a house where a set of solar panels are kept in spare for their simultaneously working when main power supply is discontinued.

scholarly journals Stochastic Analysis of a Priority Standby System under Preventive Maintenance

2021 ◽  
Vol 11 (9) ◽  
pp. 3861
Author(s):  
Khalaf S. Sultan ◽  
Mohamed E. Moshref
Keyword(s):  
Preventive Maintenance ◽  
Stochastic Analysis ◽  
Failure Modes ◽  
Reliability Measures ◽  
Partial Failure ◽  
Regenerative Point ◽  
Cold Standby ◽  
Total Failure ◽  
Standby System ◽  
Regenerative Point Technique

In this paper, we propose a system of two dissimilar units: one unit prioritizes operation (priority unit), and the other unit is kept as a cold standby (ordinary unit). In this system, we assume that the failures, repairs, and preventive maintenance (PM) times follow arbitrary distributions for both units, except for the fact that the repair time of the ordinary unit follows an exponential distribution. The priority unit has normal, partial failure or total failure modes, while the ordinary unit has normal or total failure modes. The PM of the system can be started after time t when (i) the priority unit is in the normal or partial failure modes up to time t and (ii) the standby unit is available up to time t. PM can be achieved in two types: the costlier type with probability p and the cheaper type with probability (1−p). Under these assumptions, we investigate the reliability measures of the system using the regenerative point technique. Finally, we show a numerical example to illustrate the theoretical findings and show the effect of preventive maintenance in the reliability measures of the proposed system.

RELIABILITY MEASURES OF A COLD STANDBY SYSTEM WITH PREVENTIVE MAINTENANCE AND REPAIR

2013 ◽  
Vol 20 (06) ◽  
pp. 1350022 ◽  
Author(s):  
S. C. MALIK ◽  
SUDESH K. BARAK
Keyword(s):  
Preventive Maintenance ◽  
Failure Time ◽  
Reliability Measures ◽  
Maintenance And Repair ◽  
Regenerative Point ◽  
Cold Standby ◽  
Semi Markov Process ◽  
Standby System ◽  
Regenerative Point Technique ◽  
Negative Exponential

The purpose of the present study is to determine reliability measures of a two-unit cold standby system with preventive maintenance and repair. The units are identical in nature subject to constant failure from normal mode. Preventive maintenance of the operative unit is carried out after a pre-specific time "t" up to which no failure occurs. However, repair of the unit is done at its failure. The unit works as new after repair and preventive maintenance. The switch devices are perfect. The distributions of failure time and the time by which unit undergoes for preventive maintenance are taken as negative exponential while that of preventive maintenance and repair times are assumed as arbitrary with different probability density functions. The random variables associated with failure, preventive maintenance and repair times are statistically independent. The semi-Markov process and regenerative point technique are adopted to derive the expressions for system performance measures in steady state. The graphical behavior of MTSF, availability and profit function have been observed with respect to preventive maintenance rate for particular values of other parameters and costs.

Justification for Unscheduled Maintenance of Solar Panels Used as a Power Supply for Sprinkler Machines

2020 ◽  
Vol 67 (1) ◽  
pp. 16-21
Author(s):  
Sergey M. Bakirov ◽  
Sergey S. Eliseev
Keyword(s):  
Power Supply ◽  
Power Loss ◽  
Renewable Energy Sources ◽  
Operating Mode ◽  
Dust Storms ◽  
Research Purpose ◽  
Solar Panels ◽  
Solar Module ◽  
Empirical Observation ◽  
Modern Level

The modern level of agriculture is described by the introduction of renewable energy sources. New generation sprinkler machines are being put into production, in the power system of which solar panels are used. One of the factors that negatively affect the performance of solar cells in an open field is their dusting, which is formed as a result of dust storms and wind. Cleaning of the battery panels is carried out in various ways: manual, semi-automatic and automatic. Dust cleaning is included in maintenance. (Research purpose) The research purpose is to determine the conditions for performing the maintenance, which consists in cleaning solar panels in the field. (Materials and methods) Theoretical (analysis, hypothesis design), empirical (observation, testing), experimental (ascertaining experiment) methods has been used during research. (Results and discussion) The article describes an introduced parameter for estimating the level of dusting. The power loss indicator shows the ratio of the power of the dusted module to the power of the clean module. Unscheduled maintenance is affected by the distance of the solar module from the repair point, the power of the solar module, the loss from dusting, the frequency of maintenance and cost indicators. (Conclusions) It has been found the dependence of maintenance period of the solar module of the sprinkler machine on the distance to the sprinkler machine, to the point of maintenance and repair, the power loss coefficient in case of dusting of the solar module, the cost of performing maintenance, as well as the frequency of maintenance. Article describes the boundaries of the choice of operating mode of the sprinkler between unscheduled maintenance for cleaning the solar module and the acceptance of additional power of the sprinkler power supply system according to the criterion of minimum operating costs.

On queueing systems by retrials

1983 ◽  
Vol 20 (02) ◽  
pp. 380-389 ◽  
Author(s):  
Vidyadhar G. Kulkarni
Keyword(s):  
General Result ◽  
Service Time ◽  
Queueing Systems ◽  
Single Server ◽  
Expected Number ◽  
Waiting Room ◽  
Second Moments ◽  
Different Types ◽  
General Distributions ◽  
Arbitrary Service Time

A general result for queueing systems with retrials is presented. This result relates the expected total number of retrials conducted by an arbitrary customer to the expected total number of retrials that take place during an arbitrary service time. This result is used in the analysis of a special system where two types of customer arrive in an independent Poisson fashion at a single-server service station with no waiting room. The service times of the two types of customer have independent general distributions with finite second moments. When the incoming customer finds the server busy he immediately leaves and tries his luck again after an exponential amount of time. The retrial rates are different for different types of customers. Expressions are derived for the expected number of retrial customers of each type.

scholarly journals Photovoltaic solar power for a wastewater electrocoagulation prototype

2020 ◽  
pp. 32-36
Author(s):  
Luis Alberto Cantera-Cantera ◽  
Andrés Calvillo-Téllez
Keyword(s):  
Wastewater Treatment ◽  
Power Supply ◽  
Rural Areas ◽  
Solar Power ◽  
Solar Panels ◽  
Nickel Metal ◽  
Supply Line ◽  
A Current

A photovoltaic solar power supply is presented; it supplies energy to the electrodes of a wastewater treatment prototype by electrocoagulation. The source will be able to supply three voltages levels 10, 20, and 30 volts, with a current of 1000 mA. The system consists of an array of solar panels and Nickel Metal batteries. The amount of energy to be supplied by the solar panels is estimated, the level of storage in batteries is calculated and fed to the electrocoagulation system. The results of an experiment that operates independently of the power supply line and that works in rural areas are presented.

scholarly journals Applications of Queuing Theory in Quantitative Business Analysis

2020 ◽  
pp. 253-257
Keyword(s):  
Quantitative Analysis ◽  
Waiting Time ◽  
Queuing Theory ◽  
Single Channel ◽  
Analysis Approach ◽  
Single Server ◽  
Expected Number ◽  
Queuing Model ◽  
Infinite Population ◽  
Expected Waiting Time

Queuing Theory provides the system of applications in many sectors in life cycle. Queuing Structure and basic components determination is computed in queuing model simulation process. Distributions in Queuing Model can be extracted in quantitative analysis approach. Differences in Queuing Model Queue discipline, Single and Multiple service station with finite and infinite population is described in Quantitative analysis process. Basic expansions of probability density function, Expected waiting time in queue, Expected length of Queue, Expected size of system, probability of server being busy, and probability of system being empty conditions can be evaluated in this quantitative analysis approach. Probability of waiting ‘t’ minutes or more in queue and Expected number of customer served per busy period, Expected waiting time in System are also computed during the Analysis method. Single channel model with infinite population is used as most common case of queuing problems which involves the single channel or single server waiting line. Single Server model with finite population in test statistics provides the Relationships used in various applications like Expected time a customer spends in the system, Expected waiting time of a customer in the queue, Probability that there are n customers in the system objective case, Expected number of customers in the system

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