Abstract:Purpose: In the last three decades, thousands of companies around the world have embraced the ISO 9001 standard in their quest to improve company performance and customer satisfaction. In recent literature, a number of authors have identified different "levels" of ISO 9001implementation. This study aims to analyse these implementation levels in companies from the point of view of the customer, and provide guidelines for future improvement. Findings: Auditing suppliers plays a unique role in helping to isolate system weaknesses, identify opportunities and suggest areas for improvement. This study shows that, in terms of management commitment and culture and the good practices of an organization, ISO 9001 certified companies implement differing degrees of the standard. From the results of this research, a "road map" towards improvement can be established; one that allows companies in the sector to go beyond simply being accredited with the standard and instead to take advantage of ISO 9001 certification as a catalyst for change.-1090-Journal of Industrial Engineering and Management -http://dx.doi.org/10.3926/jiem.2072Research limitations/implications: This article focuses only on the wind power sector, although its findings could be extrapolated to similar sectors of high technology and high levels of customization.Originality/value: While quality audits are a customary topic for academics and researchers, few contributions are related to SPAs and their impact on the quality control process of company suppliers. Primary data from the SPAs of suppliers (objective data collected by one of the paper's authors), was used here and is one of the most valuable aspects of this paper's contribution.
In this study, a wrapper approach was applied to objectively select the most important variables related to two different anaerobic digestion imbalances, acidogenic states and foaming. This feature selection method, implemented in artificial neural networks (ANN), was performed using input and output data from a fully instrumented pilot plant (1 m3 upflow fixed bed digester). Results for acidogenic states showed that pH, volatile fatty acids, and inflow rate were the most relevant variables. Results for foaming showed that inflow rate and total organic carbon were among the relevant variables, both of which were related to the feed loading of the digester. Because there is not a complete agreement on the causes of foaming, these results highlight the role of digester feeding patterns in the development of foaming.
Anaerobic digestion (AD) is a complex biological system which can be affected by several operational problems. Among them, biological foaming is one of the most difficult to deal with. It has many effects, such as causing gas pipe clogging and probe failures, and it can affect mixing devices, etc. Since the mechanisms involved in biological foaming development are not fully understood, it is not included in standard anaerobic digestion models. For this reason, a knowledge-based risk model to determine the suitable conditions for the development of biological foaming during AD simulation was developed. The resulting knowledgebased system, based on organic loading rate (OLR) and its daily variation, was experimentally validated using real data from a fully instrumented pilot plant (1 m 3 upflow fixed bed digester). Results show a good correlation between the knowledge-based risk model and the estimated biological foaming risk from real data.
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