摘要:

AbstractA range of process capability indices is widely used to measure process performance. The simplicity of the formulae for these capability indices is both a strength and a weakness. The underlying assumptions behind capability indices are frequently overlooked. Capability studies usually result in single point estimates which may result in misleading assessments of process performance. Point estimates ignore sampling error, and safer estimates can be obtained by constructing confidence intervals. The construction of confidence intervals is considered in some detail. Testing or measurement variability give rise to additional uncertainty in process capability assessments. Inaccurate assessments of process performance can result if the basic assumptions and sources of uncertainty are overlooked.

ISSN:0748-8017    

DOI:10.1002/qre.4680070602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper reports the results of a study carried out in one of the plants of a multi‐plant manufacturer with the objective of evaluating and analysing the quality costs to identify areas of quality improvement and quality cost reduction. The study was carried out in two phases, namely the estimation of quality costs as a ‘one‐shot’ study followed by the identification of the ‘vital few’ defects using Pareto analysis, and this was followed by a further analysis using cause‐and‐effect diagrams to find out the underlying causes of these vital defects. This case study shows that even in situations where inspection and relevant records/data are not available, the necessary data can be obtained through a step‐by‐step analysis of current procedure and methods, and collection of data with regard to defects; and the data, thus obtained, can be used for the evaluation of quality costs. Moreover, an objective analysis of category‐wise and shop‐wise quality costs, with the help of Pareto and cause‐and‐effect analyses can bring out the critical quality problems and subsequently the causes

ISSN:0748-8017    

DOI:10.1002/qre.4680070603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe reliability of HEMT ICs has been analysed when they are treated as weakly coupled dual channel systems. The separation distance between the two‐dimensional electron gas channels is the critical parameter which affects reliability. The introduction of deep traps at 0·65 eV has been shown to occur during accelerated life tests. In addition, the HEMT dual channel IC reliability results tend to follow the enhancement mode degradation statistics. All testing was carried out at 12 GHz and at channel temperatures between 130°C and 25

ISSN:0748-8017    

DOI:10.1002/qre.4680070604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractEight years of experience with quality circles has shown a progression toward the achievement of total quality. Significant positive results have led to the evolution from a voluntary programme to the implementation of a non‐voluntary programme that includes functional supervisors. Each team meets for an hour per week during normal work hours as an integral part of the job. Over 83 per cent of manufacturing and support groups employee participation has been recorded to date and at present 62 teams are functioning. This article will present the details of this programme's progress towards quality excellenc

ISSN:0748-8017    

DOI:10.1002/qre.4680070605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThis article presents a technique which allows one to choose the ‘best’ set of quality judges. The methodology can be applied to any situation requiring discernment of a qualified inspector of products or service. The approach presented in this article selects judges who align their quality criteria with the prevailing expert. Multidimensional scaling is conducted on a disagreement matrix formed by executing multiple pairwise comparisons. An example of voice quality judging is included in the article as a practical example of the techni

ISSN:0748-8017    

DOI:10.1002/qre.4680070606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractAdvanced technologies today are such that it is possible to keep the occurrence of defects in manufactured products at very low levels. The use of the conventionalc‐chart for statistical control of defects in such products would encounter serious practical difficulties because the low defect counts would render invalid the theoretical assumptions used in the construction of the chart. Based on reasoning with fundamental probability distributions, this paper offers a simple and reliable solution that is particularly suited to on‐line inspection and testing operations such as those found in an automated manufacturing environm

ISSN:0748-8017    

DOI:10.1002/qre.4680070607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractFor as long as electronic devices have been produced the relationship between the costs and benefits of quality assurance has been discussed. At present this relationship is influenced by the increase in the complexity of integrated circuits and by the growing extent of automation in production. In this paper a way is presented showing how the cost of quality assurance can be decreased without loss of quality. Six steps to achieving this goal are described.

ISSN:0748-8017    

DOI:10.1002/qre.4680070608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThis is the final installment of a series of three articles under the general topic ‘Off the bathtub onto the roller‐coaster curve’. A short version was presented at the 1988 Annual Reliability and Maintainability Symposium in the U.S.A. The first article was entitled ‘The bathtub does not hold water any more’, and the second was entitled ‘The roller‐coaster curve is in’. The three articles provide detailed discussions of the findings leading to the conclusions on the roller‐coaster characteristics for the hazard rate curve for electronics. The first article discussed the problems with the bathtub and the second explored the shape of the hazard rate curve in view of some recent observations. This article suggests some plausible physical reasons for the formation of the roller‐coaster shape. The generation of the shape starts with the basic failure mechanisms, which leads to the generally decreasing hazard rate. The humps could be caused by changing hazard conditions, wear‐out failure distribution of flawed items, distribution of flaw sizes or residue small size flaws left in the equipment because of test and i

ISSN:0748-8017    

DOI:10.1002/qre.4680070609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper describes a quantitative safety study carried out on a system which monitors the environmental conditions in an undersea mine. Of particular importance are the concentrations of methane and carbon monoxide present in the mine. Although the presence of these gases is of concern in all mines it is of particular concern in this undersea mine since up to 37 per cent of the return air of the ventilation system is recirculated. When high methane or carbon monoxide levels are detected recirculation is halted.Fault trees were constructed to represent two system failure modes for each of the trip conditions; failure to trip on demand and spurious trip. These logic diagrams were then analysed to produce the minimal cut sets and the probabilities for the system failure events. From this prediction of system performance the degree of improvement attainable by changing the system design, component repair times or test frequencies was investigated.

ISSN:0748-8017    

DOI:10.1002/qre.4680070610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

ISSN:0748-8017    

DOI:10.1002/qre.4680070611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY