Inhibition of Hydroperoxy-, Keto- and Hydroxy-FAME by Alpha- and Delta-Tocopherol at Rancimat Conditions

The effects of α‐ and δ‐tocopherol on inhibition of hydroperoxides, keto and hydroxy compounds under Rancimat conditions, i.e. 100 °C and air bubbling, were studied in samples of fatty acid methyl esters (FAME) obtained from high linoleic (HL) and high oleic (HO) sunflower oils. Primary hydroperoxides from methyl linoleate and methyl oleate and secondary keto and hydroxy compounds derived from methyl linoleate hydroperoxides were analyzed by HPLC–UV‐ELS. Different tocopherol concentrations, namely, 10, 50, 100, 500 and 1000 mg/kg, were tested. Irrespective of the lipid substrate and the initial concentration of tocopherol, results showed that the content of hydroperoxides accumulated during the induction period was remarkably higher in the samples containing δ‐tocopherol. The relative concentrations of oleate hydroperoxides in the HO samples were also higher in the presence of δ‐tocopherol. α‐Tocopherol was more effective in inhibiting hydroperoxides at low levels, with 100 mg/kg as optimal concentration, while δ‐tocopherol displayed optimal protection at 1000 mg/kg. Under the oxidation conditions applied, neither α‐ nor δ‐tocopherol showed a protective effect on hydroperoxide decomposition at any level assayed. Formation of keto‐ and hydroxy‐dienes was more related to the concentration of their hydroperoxide precursors. Furthermore, both tocopherols gave rise to increased concentrations of ketodienes at 500 and 1000 mg/kg compared to the controls. Such an effect was more pronounced for α‐tocopherol and in the HL samples.     

Simplified resubmitted lot inspection from defect counts

Nowadays, as low defect rates per item are often expected in practice, conventional single sampling for lot acceptance purposes is rendered inefficient or unduly expensive. For specific producer’s and consumer’s quality and risk requirements, resubmitted lot sampling usually needs, on the average, less inspection effort than single sampling to properly discriminate between satisfactory and unsatisfactory batches. An integer nonlinear programming problem is stated in order to determine the optimal resubmitted lot sampling plan based on defect count data with limited producer and consumer risks. Nonaccepted lots may be resubmitted for sampling inspection a certain number of times. The number of nonconformities per sampled unit is assumed to follow a Poisson distribution. Quasi-optimal inspection schemes for screening submitted lots of manufactured material are derived in closed-forms by using a normal approximation of the incomplete gamma ratio function. Explicit and quite accurate approximations of the smallest number of units to be tested per lot and the maximum tolerable number of nonconformities in the selected sample are presented. The number of resubmissions with minimal inspection effort and controlled risks is also computed. An application to the manufacturing of glass is provided for illustrative purposes.     

Expressing aspectual interactions in design: evaluating three AOM approaches in the slot machine domain

In the context of an industrial project, we evaluated the implementation of the software of a casino slot machine. This software has a significant amount of crosscutting concerns that depend on and interact with each other as well as with the modular concerns. We therefore wished to express our design using an appropriate aspect-oriented modeling approach. We therefore evaluated three candidate methodologies: Theme/UML, WEAVR, and RAM to establish their suitability. Remarkably, only the last of the three has shown to allow an adequate expression of the interactions, albeit not fully explicit. The first two fall short because half of the interaction types cannot be expressed at all while the other half need to be expressed using a work-around that hides the intention of the design. Neither does RAM allow a fully explicit expression of interactions, but it would be the most adequate approach for the slot machine case.     

Effective absorption coefficient for graded band-gap semiconductors and the expected photocurrent density in solar cells

A simple model for the generation of carriers by photons incident on a (linearly) decreasing band-gap material, such as has been described in recent CIGS solar cells, is developed. The model can be generalized for different cases such as increasing band-gap grading or for having a more complex band-gap profile.The model developed for direct band semiconductors such as CIGS or AlGaAs allows us to define an effective absorption coefficient, so that the ideal photocurrent density can be calculated in a similar manner as for solar cells with non-graded band-gap materials.We show that this model gives completely different results as those expected from intuitive approaches for calculating this ideal photocurrent density. We also show that grading of the band-gap of the absorbing material in solar cells makes the photocurrent less sensitive to the total band-gap change, in such a way that the design of the band-gap variation can be more flexible in order to have other advantages such as higher built-in voltage or higher back surface field in the device structure.