Comparison of two models for managing reliability growth during product design

Relying on reliability growth testing to improve system designis neither usually effective nor efficient. Instead it is importantto design in reliability. This requires models to estimate reliabilitygrowth in the design that can be used to assess whether goalreliability will be achieved within the target timescale forthe design process. Many models have been developed for analysisof reliability growth on test, but there has been much lessattention given to reliability growth in design. This paperdescribes and compares two models: one motivated by the practicalengineering process; the other by extending the reasoning ofstatistical reliability growth modelling. Both models are referencedin the recently revised edition of international standard IEC61164. However, there has been no reported evaluation of theirproperties. Therefore, this paper explores the commonalitiesand differences between these models through an assessment oftheir logic and their application to an industrial example.Recommendations are given for the use of reliability growthmodels to aid management of the design process and to informproduct development.     

Cost–benefit modelling for reliability growth

Decisions during the reliability growth development process of engineering equipment involve trade-offs between cost and risk. However slight, there exists a chance an item of equipment will not function as planned during its specified life. Consequently the producer can incur a financial penalty. To date, reliability growth research has focussed on the development of models to estimate the rate of failure from test data. Such models are used to support decisions about the effectiveness of options to improve reliability. The extension of reliability growth models to incorporate financial costs associated with ‘unreliability’ is much neglected. In this paper, we extend a Bayesian reliability growth model to include cost analysis. The rationale of the stochastic process underpinning the growth model and the cost structures are described. The ways in which this model can be used to support cost–benefit analysis during product development are discussed and illustrated through a simple case.     

Challenges in the structural characterization of thin organic films

This review addresses the special problems associated with the micro-structural characterization of thin and ultrathin organic films, primarily by optical spectroscopies. Films which are deposited by Langmuir-Blodgett techniques, self-assembly chemistry, and bulk film deposition techniques are considered. The use of enhanced optical excitation using surface phasma resonances and integrated optical structures is discussed extensively, as is the use of ellipsometry. Discussion of the spectroscopies used is broken into a section on electronic spectroscopies and an extensive discussion of vibrational spectroscopies. Vibrational information may be obtained with photons (absorption or scattering) or electrons (loss spectra), and the types of experimental systems amenable to each, along with the advantages and disadvantages of each are explored.     

Isolation of Alicyclobacillus acidoterrestris from fruit juices

K agar, a novel isolation medium developed for the food industry, was compared with other acidified media for isolation of Alicyclobacillus acidoterrestris spores. Spores were inoculated into apple juice, orange juice, and a fruit juice blend and then isolated on the following media: K agar, pH 3.7; semi-synthetic medium, pH 4.0; orange serum agar, pH 3.5; and minimal salts medium, pH 4.0. Media were incubated at 24, 35, 43, and 55 degrees C. Highest recovery of spores was obtained with either K agar or semi-synthetic medium, incubated at 43 degrees C. The effect of heat shocking spores at different times was also determined; heat shocking at 80 degrees C for 10 min was considered appropriate. Peptone, previously shown to inhibit A. acidoterrestris, was not inhibitory when present in K agar. A collaborative trial with 9 laboratories was undertaken to determine the repeatability and reproducibility of counts on K agar. K agar prepared from individual components was compared with dehydrated K agar prepared by International BioProducts (Redmond, WA). There were no significant differences between log mean counts for the 2 media for each of the juices analyzed at both the high and the low inoculum levels. Repeatability and reproducibility values were not significantly different either within juices, within trials, or across all samples tested in both trials. K agar is suitable for isolation of A. acidoterrestris spores from fruit juices.     

Sizable concentration-dependent frequency shifts in solution NMR using sensitive probes

With the growing use of high fields and ultrasensitive probes, radiation damping emerges as a significant feedback interaction in modern solution NMR. Motivated by recent observations of mysterious concentration-dependent frequency shifts, experiments carried out on a cryoprobe at 600 MHz have revealed a time-averaged frequency shift of up to +83/-81 Hz. The sizable frequency shifts arise from deviations in the phase of the radiation damping field from perfect orthogonality relative to the net transverse magnetization. The frequency shift is shown to depend on the longitudinal magnetization and probe tuning conditions through experiments and numerical simulations. Such unexpected shifts in the solvent precession frequency provide a physical explanation for the empirical practice of adjusting the irradiation frequency of the saturating B1 field in solvent presaturation to achieve optimal suppression. Additional applications of the radiation damping induced frequency shift to solvent suppression and NMR methodology are discussed.     

Supplier quality improvement: The value of information under uncertainty

We consider supplier development decisions for prime manufacturers with extensive supply bases producing complex, highly engineered products. We propose a novel modelling approach to support supply chain managers decide the optimal level of investment to improve quality performance under uncertainty. We develop a Poisson–Gamma model within a Bayesian framework, representing both the epistemic and aleatory uncertainties in non-conformance rates. Estimates are obtained to value a supplier quality improvement activity and assess if it is worth gaining more information to reduce epistemic uncertainty. The theoretical properties of our model provide new insights about the relationship between the degree of epistemic uncertainty, the effectiveness of development programmes, and the levels of investment. We find that the optimal level of investment does not have a monotonic relationship with the rate of effectiveness. If investment is deferred until epistemic uncertainty is removed then the expected optimal investment monotonically decreases as prior variance increases but only if the prior mean is above a critical threshold. We develop methods to facilitate practical application of the model to industrial decisions by a) enabling use of the model with typical data available to major companies and b) developing computationally efficient approximations that can be implemented easily. Application to a real industry context illustrates the use of the model to support practical planning decisions to learn more about supplier quality and to invest in improving supplier capability.     

Taking a strategic view of BPR to develop a multidisciplinary framework

Despite undoubtedly being one of the latest fads, Business Process Reengineering (BPR) has provoked much debate about how organisations should be managed if dramatic improvements in performance are to be achieved. This paper takes a multidisciplinary view of BPR and focuses upon a number of the emergent issues. These include the role of strategy making, the promotion of communication and creativity, the role of statistics, and the effective use of performance measurement systems within a learning environment. The paper develops a framework that capitalises on the role of modelling in MS/OR as well as the various disciplines of the authors. As such, the framework draws on recent advances, as well as established thinking, in the areas of strategy development, information systems, quality management and statistical science. More importantly, the framework also provides an iterative approach to BPR enabling organisations to design, implement and monitor progress on an ongoing basis. Emphasis is placed on building effective communications, developing an organisational memory and supporting organisational learning.