| 1. |
- Ahmadi, Alireza, et al.
(author)
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Estimation of economic consequences of aircraft system failures
- 2012
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In: Communications in Dependability and Quality Management. - 1450-7196. ; 15:1, s. 39-49
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Journal article (peer-reviewed)abstract
- A large portion of the direct and indirect aircraft operational costs stems from the consequences of decisions made during the maintenance program development. Decision on maintenance task selection for non-safety category of failures, is based on the cost effectiveness, in which the cost of preventive maintenance should be less than the costs associated with the corrective action and failure consequence. Although the assessment of the direct cost for preventive and corrective maintenance is quiet straightforward, however quantification and estimation of the cost associated with the consequence of failure is a great challenge. This is due to a long list of contributory factors and lack of adequate data regarding the cost headings. This study attempts to estimate the economic consequences of aircraft system failures which lead to a technical delay. The paper considers financial losses, mostly due to the additional unexpected costs related to the flight crew, passengers, aircraft itself, ramp and airport, when one of the cost headings, e.g. the pre-fixed crew cost is known. The experience of the field experts has been used following a pairwise comparison technique to compare the cost headings, and to estimate the contribution of each one to the total cost of a delay. The study shows that the proposed model can be a tool to assess the cost of failure consequences in aircraft operation, when there is a limited data and information regarding the cost headings.
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| 2. |
- Grundén, Kerstin, 1952-
(author)
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Evaluation of the Development Process of a CSCW System for Health Care Planning
- 2008
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In: Communication in Dependability and Quality Management International Journal (CDQM). - Cacak, Serbien : CDQM Research Centre. - 1450-7196. ; 11:1, s. 87-97
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Journal article (peer-reviewed)abstract
- In this article an evaluation study of the development and test of a CSCW system for health care planning, is reported. The system supports the co-operative health care planning process for hospital care, primary care and municipality organised care. A CSCW system often affect informal aspects of work, and the use of the evaluation model MOA-E contributed to explain the logics of a CSCW system focussing on both work situation of the individuals, work process and quality produced to the patients. The system development was criticised for taking too long time by the stakeholders. They did not seem to understand the special characteristics of developing a CSCW system compared with a more traditional system. The evaluation model contributed to explain for the long time used for developing the system. Interviews with test users focussed their experiences of the development process. Much time has been spent on analysis of the work routines in the development work in an iterative “learning by doing” process. This participate development work has served as a learning process for the participants. The participative development style seems to be relevant for CSCW systems, but is more time consuming compared with traditional systems development.
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| 3. |
- Ahmadi, Alireza, et al.
(author)
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Selection of maintenance strategy, using analytical hierarchy process
- 2009
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In: Communications in Dependability and Quality Management. - 1450-7196. ; 12:1, s. 121-132
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Journal article (peer-reviewed)abstract
- Selection of appropriate maintenance strategy is key to economic viability of aviation and manufacturing industries. The study discusses and presents an approach to facilitate the selection of the most appropriate maintenance strategy on the basis of the cost-benefit analysis by using Analytical Hierarchical Process (AHP). The goal is to select the most cost-effective alternative, among Run-To-Failure (RTF), Preventive Maintenance (PM), incorporating Prognostic Health Management(PHM) capability, or any possible Design-Out Maintenance (DOM) strategies, which positively affects on aircraft operational availability. In this paper we proposed a stepwise algorithm to guide the selection process, based on two criteria of operational availability (benefit) and cost of failure.
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| 4. |
- Galar, Diego, et al.
(author)
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Risk Based Maintenance policies for SMART devices
- 2013
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In: Communications in Dependability and Quality Management. - 1450-7196. ; 16:3, s. 15-28
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Journal article (peer-reviewed)abstract
- Maintenance activities are commonly organized into scheduled and unscheduled actions. Scheduled maintenance is undertaken during pre-programmed inspections. Such maintenance operations try to minimize the risk of deterioration based on a priori knowledge of failure mechanisms and their timing. However, in complex systems it is not always possible to schedule maintenance actions to mitigate all undesired effects, and SMART systems, which monitor selected parameters, propose actions to correct any deviation in normal behavior. Maintenance decisions must be made on the basis of accepted risk. Performed or not performed scheduled tasks as well as deferred corrective actions can have positive or negative consequences for the company, technicians and machines. These three risks should be properly assessed and prioritized as a function of the goals to be achieved. This paper focuses on how best practices in risk assessment for human safety can be successfully transferred to risk assessment for asset integrity.
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| 5. |
- Garmabaki, Amir Soleimani, et al.
(author)
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The Optimal Time of New Generation Product in the Market
- 2012
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In: Communications in Dependability and Quality Management. - 1450-7196. ; 15:1, s. 123-137
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Journal article (peer-reviewed)abstract
- Most product development activities are aimed at improving existing products by successive generation policy. The launch of a new product is a phase of development that commands a large commitment of time, money, and managerial resources. Determination of optimal introduction time is especially critical for high-technology products, where the introduction of each successive generation of a product requires the firm to explicitly consider its impact on the demand for preceding generations. Each generation has unique expectations, experiences, generational history, lifestyles, values, and demographics that influence behavior of potential buyers. Accordingly, many companies are reaching out to multi-generational consumers and trying to understand and gain the attention of these diverse buyers. The timing decision depends on whether companies invest more time for product design or push the product to market before maturity. The study identifies attributes such as Customer's Adoption Indicator and Cost that affect the introduction time of new generation. To trade-off between two decision factors, multi-attribute utility theory (MAUT) is applied in our decision space. We examine the case where a firm introduces successive generations of a durable product for which demand is characterized by an innovation diffusion process. Empirical implications of the proposed model have been validated on data collected from two industries (Semiconductor Industry DRAM shipments and IBM Mainframe Industry (USA)).
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| 6. |
- Kapur, P.K., et al.
(author)
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Optimal price and warranty length
- 2012
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In: Communications in Dependability and Quality Management. - 1450-7196. ; 15:1, s. 5-13
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Journal article (peer-reviewed)abstract
- With rapid advancement in technologies in the last few decades organizations today have shifted their focus from being product centric to customer/market driven. With post sales services like providing warranty playing an influential role in the purchase of new product, manufacturers today are leaning towards optimizing warranty length & price of their products in order to ensure profitability. In this paper treating optimal warranty length and price of goods as decision variables, we intend to maximize overall profit for producers under the influence of a combination of free replacement and pro-rata warranty policies. Two-dimensional innovation diffusion model incorporating both price and warranty length is employed to demonstrate product sales cycle. Exponential distribution is used to represent the lifetime of a product. To elucidate application of the model real data set is presented as illustration.
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| 7. |
- Rodriguez, Emilio, et al.
(author)
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Safety Issues of Track Circuits – A Hybrid Approach
- 2014
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In: Communications in Dependability and Quality Management. - 1450-7196. ; 17:2, s. 15-26
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Journal article (peer-reviewed)abstract
- The study of railway electromagnetic interference (EMI) seeks to determine the source of the interference or to ensure the correct operation of the equipment within adverse conditions. The complexity of railway system increases when more electronics are used. However a simple DC track circuit is still used in train detection systems in many countries, including Sweden, our case study. Most of the failures reported in the Swedish railway infrastructure are related to the detection system, making this research of interest to the railway community. By searching the Swedish failures report database, 0FELIA, for the most repetitive and probable causes of failures, they were identified three worst case scenarios: low resistance between the rails, external interference as a lightning and iron-powder-bridges in the insulated joint. They were simulated using the software CST STUDIO SUITE® (Computer Simulation Technology Studio Suite), supported by real measurements on site. Measurements followed the current EMC standards and were used to tune and validate the models, resulting in simulations very close to the real measures.
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| 8. |
- Thaduri, Adithya, et al.
(author)
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Degradation modelling of voltage comparator using modified physics of failure approach
- 2012
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In: Communications in Dependability and Quality Management. - 1450-7196. ; 15:1, s. 76-87
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Journal article (peer-reviewed)abstract
- There are several electronic systems running continuously to control and monitor the various activities in the nuclear industry and reliability and safety of these systems is taken care of utmost importance. The Neutron Flux Monitoring System has individual electronic components is one of the modules present in the signal processing unit. This unit consists of numerous components such as Optocoupler, Constant fraction discriminator, Voltage Comparator, Instrumentation Amplifier etc., and this paper studies the degradation aspects of the Voltage comparator. The prediction of reliability was conducted at earlier phases of electronics but in the present advances in the technology that methods were no longer obsolete. Hence, the other alternative, physics of failure approach laid emphasis on the root cause analysis and degradation of the performance parameters. Apart from that, we combined physics of failure approach with the statistical methods such as Design of Experiments, Accelerated testing and failure distribution models to quantify time to failure of this electronic component by radiation and temperature as stress parameters. The degradation of the performance parameter is modelled and compared using regression analysis, parametric analysis, several response plots and response surface method.
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| 9. |
- Thaduri, Adithya, et al.
(author)
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Support vector regression degradation modeling for constant fraction discriminator
- 2012
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In: Communications in Dependability and Quality Management. - 1450-7196. ; 15:1, s. 101-122
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Journal article (peer-reviewed)abstract
- In the nuclear industries, the electronic signal processing unit plays a key role in the data processing, data analysis, control mechanism and more importantly safety of the nuclear reactor. The processing unit comprises of different modules that process pulse and current signals from detector and constant fraction discriminator which has higher criticality is one of them. Earlier the reliability was calculated using MilHdbk 217 standard and found discrepancies to the field failure. This paper studies the failure phenomenon using physics of failure approach by studying degradation and failure analysis and conducting the experiments using modified physics of failure methodology. Support vector machine (SVM) is a machine learning phenomenon using statistical learning theory. In this paper, failure data is fed to SVM for regression models intended for life prediction. From the parametric analysis, it was found that Sequential minimal optimization with RBF kernel represent the best model for degradation of the CFD. This method provides higher accuracy compared to response surface methodology.
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