Multi-state System Availability Model of Electricity Generation for a Cogeneration District Cooling Plant

2011 ◽  
Vol 4 (4) ◽  
pp. 431-438 ◽  
Author(s):  
Mohd Amin Abd Majid ◽  
Meseret Nasir
Keyword(s):  
Electricity Generation ◽  
State System ◽  
System Availability ◽  
Availability Model

scholarly journals Availability Analysis of Software Systems with Rejuvenation and Checkpointing

Mathematics ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 846
Author(s):  
Junjun Zheng ◽  
Hiroyuki Okamura ◽  
Tadashi Dohi
Keyword(s):  
Steady State ◽  
Human Error ◽  
System Modeling ◽  
Regenerative Process ◽  
State System ◽  
Software Systems ◽  
System Availability ◽  
Software Rejuvenation ◽  
Availability Analysis ◽  
Availability Model

In software reliability engineering, software-rejuvenation and -checkpointing techniques are widely used for enhancing system reliability and strengthening data protection. In this paper, a stochastic framework composed of a composite stochastic Petri reward net and its resulting non-Markovian availability model is presented to capture the dynamic behavior of an operational software system in which time-based software rejuvenation and checkpointing are both aperiodically conducted. In particular, apart from the software-aging problem that may cause the system to fail, human-error factors (i.e., a system operator’s misoperations) during checkpointing are also considered. To solve the stationary solution of the non-Markovian availability model, which is derived on the basis of the reachability graph of stochastic Petri reward nets and is actually not one of the trivial stochastic models such as the semi-Markov process and the Markov regenerative process, the phase-expansion approach is considered. In numerical experiments, we illustrate steady-state system availability and find optimal software-rejuvenation policies that maximize steady-state system availability. The effects of human-error factors on both steady-state system availability and the optimal software-rejuvenation trigger timing are also evaluated. Numerical results showed that human errors during checkpointing both decreased system availability and brought a significant effect on the optimal rejuvenation-trigger timing, so that it should not be overlooked during system modeling.

scholarly journals Methodology for the Assessment of Imprecise Multi-State System Availability

Mathematics ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 150
Author(s):  
Joanna Akrouche ◽  
Mohamed Sallak ◽  
Eric Châtelet ◽  
Fahed Abdallah ◽  
Hiba Hajj Chehade
Keyword(s):  
Markov Chains ◽  
Constraint Propagation ◽  
State System ◽  
Combined Approach ◽  
System Availability ◽  
Contraction Method ◽  
Numerical Examples ◽  
Complex Architectures ◽  
Backward Propagation ◽  
Interval Constraint

Most existing studies of a system’s availability in the presence of epistemic uncertainties assume that the system is binary. In this paper, a new methodology for the estimation of the availability of multi-state systems is developed, taking into consideration epistemic uncertainties. This paper formulates a combined approach, based on continuous Markov chains and interval contraction methods, to address the problem of computing the availability of multi-state systems with imprecise failure and repair rates. The interval constraint propagation method, which we refer to as the forward–backward propagation (FBP) contraction method, allows us to contract the probability intervals, keeping all the values that may be consistent with the set of constraints. This methodology is guaranteed, and several numerical examples of systems with complex architectures are studied.

Performance and Cost Assessment of a Small Solar Photovoltaic System Using Gumbel-Haugaard Family Copula Analysis

2021 ◽  
Author(s):  
Anas Maihulla ◽  
Ibrahim Yusuf ◽  
Saminu Bala
Keyword(s):  
Sensitivity Analysis ◽  
Photovoltaic System ◽  
Cost Assessment ◽  
Time To Failure ◽  
Solar Photovoltaic ◽  
Schematic Diagram ◽  
System Availability ◽  
Solar Photovoltaic System ◽  
Mean Time ◽  
Availability Model

Abstract The main objective of the present study is to analyze the availability of solar photovoltaic system. The solar photovoltaic system in this paper is simple one consisting of four subsystems namely, solar panel subsystem, charge controller subsystem, batteries subsystem and inverter subsystem. Through the schematic diagram of state of the system, availability model is formulated and Chapmen - Kolmogorov differential equations are developed and solved using Gumbel Haugaard family Copula technique. The numerical values for availability, reliability, mean time to failure (MTTF), cost analysis as well as sensitivity analysis are presented. The effects of failure rates to various solar photovoltaic subsystems were developed.

Structure function in analysis of multi-state system availability

2018 ◽  
pp. 897-905
Author(s):  
M. Kvassay ◽  
V. Levashenko ◽  
J. Rabcan ◽  
P. Rusnak ◽  
E. Zaitseva
Keyword(s):  
Structure Function ◽  
State System ◽  
System Availability

Markovian Availability Measurement and Assessement for Hardware-Software System

1997 ◽  
Vol 04 (03) ◽  
pp. 257-268 ◽  
Author(s):  
Koichi Tokuno ◽  
Shigeru Yamada
Keyword(s):  
System Reliability ◽  
Software Systems ◽  
Software System ◽  
Reliability Growth ◽  
System Availability ◽  
Software Failures ◽  
Software Failure ◽  
Dependent Behavior ◽  
Reliability Performance ◽  
Availability Model

It is important to take into account the trade-off between hardware and software systems when total computer-system reliability/performance are evaluated and assessed. We develop an availability model for a hardware-software system. The system treated here consists of one hardware subsystem and one software subsystem and it is assumed that the system is down and restored whenever a hardware or a software failure occurs. Especially, for the software subsystem, it is supposed that (i) the restoration actions are not always performed perfectly, (ii) the restoration times for later software failures become longer and (iii) reliability growth occurs in the perfect restoration action. The hardware and the software failure-occurrence phenomena are respectively described by constant and geometrically decreasing hazard rates. The time-dependent behavior of the system, which alternately repeats the operational state that a system is operating without failures and the restoration state that a system is inoperable and restored, is described by a Markov process. Useful expressions for several quantitative measures of system performance are derived from this model. Finally, numerical examples are presented for illustration of system availability measurement and assessment.

scholarly journals A Comprehensive Availability Modeling and Analysis of a Virtualized Servers System Using Stochastic Reward Nets

2014 ◽  
Vol 2014 ◽  
pp. 1-18 ◽  
Author(s):  
Tuan Anh Nguyen ◽  
Dong Seong Kim ◽  
Jong Sou Park
Keyword(s):  
Sensitivity Analysis ◽  
Virtual Machine ◽  
Failure Modes ◽  
Virtual Machine Monitor ◽  
System Availability ◽  
Modeling And Analysis ◽  
New Finding ◽  
Hardware Faults ◽  
Availability Modeling ◽  
Availability Model

It is important to assess availability of virtualized systems in IT business infrastructures. Previous work on availability modeling and analysis of the virtualized systems used a simplified configuration and assumption in which only one virtual machine (VM) runs on a virtual machine monitor (VMM) hosted on a physical server. In this paper, we show a comprehensive availability model using stochastic reward nets (SRN). The model takes into account (i) the detailed failures and recovery behaviors of multiple VMs, (ii) various other failure modes and corresponding recovery behaviors (e.g., hardware faults, failure and recovery due to Mandelbugs and aging-related bugs), and (iii) dependency between different subcomponents (e.g., between physical host failure and VMM, etc.) in a virtualized servers system. We also show numerical analysis on steady state availability, downtime in hours per year, transaction loss, and sensitivity analysis. This model provides a new finding on how to increase system availability by combining both software rejuvenations at VM and VMM in a wise manner.

scholarly journals Reliability Assessment of the Transport System, Addis Ababa Case Study

2019 ◽  
Vol 49 (4) ◽  
pp. 27-36
Author(s):  
Frehaileab Admasu Gidebo ◽  
Janusz Szpytko
Keyword(s):  
Transport System ◽  
Addis Ababa ◽  
Technical Condition ◽  
Climatic Conditions ◽  
Transport Infrastructure ◽  
System Availability ◽  
Legal Provisions ◽  
Random Events ◽  
Availability Model

Abstract The subject of the article is the method of assessing the reliability of the transport system on the example of Addis Ababa in Ethiopia. The transport system and its technical condition, transport infrastructure, organization of the transport system, environment (users, environmental and climatic conditions), and legal provisions, have a significant impact on the reliability of the transport system. The most common means of transport in Addis Ababa is a car (including: taxis and minibuses). An important problem in public transport is the long waiting time for the vehicles, resulting from random events accompanying transportation processes in a defined infrastructure with limited resources. The article presents also the concept of a transport system availability model for developing countries on the example of Addis Ababa in Ethiopia.

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