| 1. |
- Ahmadi, Alireza, et al.
(författare)
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Selection of maintenance strategy for aircraft systems using multi-criteria decision making methodologies
- 2010
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Ingår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE). - 0218-5393. ; 17:3, s. 223-243
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Tidskriftsartikel (refereegranskat)abstract
- This paper, proposes the Multi-Criteria Decision Making (MCDM) methodology for selection of a maintenance strategy to assure the consistency and effectiveness of maintenance decisions. The methodology is based on an AHP-enhanced TOPSIS, VIKOR and benefit-cost ratio, in which the importance of the effectiveness appraisal criteria of a maintenance strategy is determined by the use of AHP. Furthermore, in the proposed methodology the different maintenance policies are ranked using the benefit-cost ratio, TOPSIS and VIKOR. The method provides a basis for consideration of different priority factors governing decisions, which may include the rate of return, total profit, or lowest investment. When the preference is the rate of return, the benefit-cost ratio is used, and for the total profit TOPSIS is applied. In cases where the decision maker has specific preferences, such as the lowest investment, VIKOR is adopted. The proposed method has been tested through a case study within the aviation context for an aircraft system. It has been found that using the methodology presented in the paper, the relative advantage and disadvantage of each maintenance strategy can be identified in consideration of different aspects, which contributes to the consistent and rationalized justification of the maintenance task selection. The study shows that application of the combined AHP, TOPSIS, and VIKOR methodologies is an applicable and effective way to implement a rigorous approach for identifying the most effective maintenance alternative.
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| 2. |
- Deleryd, Mats, et al.
(författare)
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Process capability studies for short production runs
- 1998
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Ingår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE). - 0218-5393. ; 5:4, s. 383-401
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Tidskriftsartikel (refereegranskat)abstract
- The current trend in modern production is directed towards shorter and shorter production runs. The two major reasons causing this trend are the rapid spread of the just in time (JIT) philosophy and the constantly increasing multiplicity of customer demands. The short runs of modern production not only constitute a challenge for production management, but they also cause some problems when applying traditional statistical methods, designed to be used for large sets of data. One of these methods is process capability studies. Since theories on how to use process capability studies in short production environments are incomplete, the aim of this paper is to present some ideas which will partly fill this gap. The theories of process capability studies for short runs presented are based on ideas of focusing on the process, not on the products, and on using data transformation. By using the transformation presented, it is possible to conduct process capability studies in a traditional straightforward manner. A simulation study shows that the suggested transformation technique works satisfactorily in real situations. Finally, the ....-plot is introduced as a method of interpreting and analyzing the capability of a short run production process. By using the .... -plot, additional information is obtained concerning the capability of a process, compared to using traditional process capability indices only.
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| 3. |
- Ekdahl, F., et al.
(författare)
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Introducing domain knowledge for selection of active factors in designed experiments
- 2000
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Ingår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE). - 0218-5393. ; 7:4, s. 341-356
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Tidskriftsartikel (refereegranskat)abstract
- Unreplicated factorial designs are widely used for designed experimentation in industry. In the analysis of designed experiments, the experimental factors influencing the response must be identified and separated from those that do not. An abundance of procedures intended to perform this selection have been introduced in the literature. A recent study indicated that the procedure due to Box and Meyer outperforms the lot of the other selection procedures in terms of efficiency and robustness. The procedure of Box and Meyer rests on a quasi-Bayesian foundation and utilizes generic domain knowledge, in the form of a common-for-all-factors a priori probability, that a factor significantly influences the response, to calculate an a posteriori probability for each factor. This paper suggests a strategy for introducing more elaborate domain knowledge about the experimental factors in the procedure of Box and Meyer, aiming to further improve its performance.
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| 4. |
- Flammini, Francesco, Senior Lecturer, 1978-, et al.
(författare)
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A multiformalism modular approach to ertms/etcs failure modeling
- 2014
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Ingår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE). - : World Scientific. - 0218-5393. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- European Railway Traffic Management System/European Train Control System (ERTMS/ETCS) is a recent standard aimed at improving performance, safety and inter-operability of modern railways. In order to be compliant to ERTMS/ETCS, a railway signalling system must meet strict nonfunctional requirements on system level failure modes. In this paper, a multiformalism model is employed to perform an availability analysis of an ERTMS/ETCS reference architecture at early phases of its development cycle. At this aim, a bottom-up analysis is performed from subsystem failure models (expressed by means of Generalized Stochastic Petri Nets, Fault Trees and Repairable Fault Trees) up to the overall system model. The modular approach, here used, allows to evaluate the influence of basic design parameters on the probability of system-level failure modes and demonstrates that system availability is within the bound required by the ERTMS/ETCS specification. The results show that the multiformalism modeling approach helps to cope with complexity, eases the verification of availability requirements and can be successfully applied to the analysis of complex critical systems. © 2014 World Scientific Publishing Company.
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| 5. |
- Garmabaki, Amir H. Soleimani, et al.
(författare)
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Modeling two-dimensional software multi-upgradation and related release problem : a multi attribute utility approach
- 2012
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Ingår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE). - 0218-5393. ; 19:3
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Tidskriftsartikel (refereegranskat)abstract
- The today's fast-paced, competitive environment in the field of Science and Technology, demands highly reliable hardware and software in order to achieve new breakthroughs in quality and productivity. In this scenario, first release of software products includes enough features and functionality to make it useful for the customers. Later, software companies have to come up with upgradation or add-ons in their software to survive in the market through a series of releases. Each succeeding upgradation offers some innovative performance or new functionality, distinguishing itself from the past releases. In one-dimensional Software Reliability Growth Models (SRGM) researcher used one factor such as Testing-Time, Testing-Effort or Coverage, etc. but within a two-dimensional SRGM environment, the process depends on two-types of reliability growth factors like Testing-time and Testing-effort. In addition, we also consider the combined effect of bugs encountered during testing of present release and user reported bugs from the operational phase. The model developed in the paper takes into consideration the testing and the operational phase where fault removal phenomenon follows, logistic and Weibull model, respectively. The paper also comprises of formulating an optimal release problem based on Multi-Attribute Utility Theory (MAUT). Lastly, the model validation is done on real dataset of software already released in the market with successive generations.
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| 6. |
- Garmabaki, Amir Soleimani, et al.
(författare)
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Predicting software reliability in a fuzzy field environment
- 2013
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Ingår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE). - 0218-5393. ; 20:3
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Tidskriftsartikel (refereegranskat)abstract
- The testing-development phase has been carried out in a given control environment. However, the product will be used in different operating environment by different end-users, which is unknown to the developer. The operating environment may range from a very clean one up to a harsh environment. These uncertain operating environments will impact to the reliability and performance of the software which may differ from the testing phase reliability. We consider that the effect of environment on reliability has a fuzzy nature. The fuzzy effects of the field environments can be captured by a unit-free environmental factor. To overcome this problem, the fuzzy probabilistic theory may be used in the processing of stochastic parameters, taking into account their fuzzy nature. The proposed model is based on Weibull distribution. The aim of this paper is to introduce a fuzzy field environment (FFE) reliability model that covers both the testing and operating phases in the development cycle. Illustration examples of the proposed model have been validated on data collected from two industries. © 2013 World Scientific Publishing Company.
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| 7. |
- Ghodrati, Behzad, et al.
(författare)
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Spare parts estimation for machine availability improvement addressing its reliability and operating environment : case study
- 2013
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Ingår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE). - 0218-5393. ; 20:3
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Tidskriftsartikel (refereegranskat)abstract
- Industrial operation cost analysis shows that, in general, maintenance represents a significant proportion of the overall operating costs. Therefore, the improvement of maintenance follows the final goal of any company, namely, to maximize profit. This paper studies spare parts availability, an issue of the maintenance process, which is an important way to improve production through increased availability of functional machinery and subsequent minimization of the total production cost. Spare parts estimation based on machine reliability characteristics and operating environment is performed. The study uses an improved statistical-reliability (S-R) approach which incorporates the system/machine operating environment information in systems reliability analysis. For this purpose, two methods of Poisson process and renewal process are introduced and discussed. The renewal process model uses a multiple regression type of analysis based on Cox’s proportional hazards modeling (PHM). The parametric approaches with baseline Weibull hazard functions and time independent covariates are considered, and the influence of operating environment factors on this model is analyzed. The outputs represent a significant difference in the required spare parts estimation when considering or ignoring the influence of the relevant system operating environment. The difference is significant in the sense of spare parts forecasting and inventory management which can enhance the parts and consequently machine availability, leading to economical operation and savings.
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| 8. |
- Hoseinie, Hadi, et al.
(författare)
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Monte Carlo reliaility simulation of water system of longwall shearer machine
- 2013
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Ingår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE). - 0218-5393. ; 20:6
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Tidskriftsartikel (refereegranskat)abstract
- The water system of coal shearer machine consists of three main subsystems namely spray jets, water & hoses, and filters which are connected and working in series configuration. In this paper the Kamat-Riley Monte Carlo simulation method was used for reliability analysis of the considered system. The studied data was collected from an Iranian longwall coal mine for analysis. The MATLAB software was used for simulation and then reliability plot of water system in shearer machine was determined. The results show that the reliability of shearer machine reduces to almost zero in a period of 300h. Comparison between the results of analytical method and simulated reliability plot presents that for analyzed data set, in high reliability levels (28%≤), the simulation approach estimates the higher reliability than analytical method. The maximum difference between the results of analytical and simulation methods is 23%. However, in low reliability levels (≤28%) there is no remarkable difference between the methods.
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| 9. |
- Hoseinie, Hadi, et al.
(författare)
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Reliability-centered maintenance for spray jets of coal shearer machine
- 2013
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Ingår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE). - 0218-5393. ; 20:3
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Tidskriftsartikel (refereegranskat)abstract
- Spray jets constitute one of the most important parts of each type of rock cutting machine, especially the drum shearer. This system cools the cutting picks and controls the dust emission. The blockage of spray jets causes the coal shearer machine to stop automatically. Therefore, the reliable performance of this system assists the achievement of a smooth coal cutting operation. Field's data shows that the maintenance of this system is time-consuming and causes major downtimes in the production process. Therefore, it is essential to find an optimum preventive maintenance task and intervals, to reduce the downtime and minimize the associated costs of the machine. The aim of this paper is to identify an applicable and effective maintenance task, with its associated interval, for management of the failure modes of the spray jets of coal shearers. A case study has been conducted on spray jets of double-drum shearer machine in Tabas Coal Mine in Iran. In the study, the RCM approach is used to select an applicable and effective maintenance task. The failure data were analyzed using a parametric approach to evaluate the reliability of the spray jets, and to estimate the reliability parameters. A reliability-based cost modeling has been implemented to identify the optimum maintenance interval and frequencies of restoration for the spray jets. In the study, a cost rate function (CRF) has been introduced in which an as-good-as-new (AGAN) effectiveness for restoration actions is considered. The CRF also considers restoration and repair times, and takes into account the costs associated with repair and restoration, and the opportunity cost of the equipment's lost production due to maintenance downtime, to arrive at the most cost-effective maintenance intervals. The results of the analysis have shown that the minimum cost per unit of time, $46.5/h, will be achieved within a range of intervals i.e., T = 210 h to T = 260 h.
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| 10. |
- Kapur, P.K., et al.
(författare)
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Foreword
- 2013
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Ingår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE). - 0218-5393. ; 20:3, s. 1-2
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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