Thermal Stress Analysis in Particulate Composite Components

Abstract: Thermal stresses resulting from flow of hot and cold water were obtained in sinks manufactured with acrylic casting dispersions by both experimental and numerical analysis. The experimental work was performed in two poly(methyl methacrylate) (PMMA) -silica based particulate composites, compositions of which are different by the volume fraction of filler and the particle size. The thermal stresses in sinks were obtained using strain gauges. The alternate flow of cold and hot water using a mixed tap, results in the formation of thermal gradients, leading to the occurrence of thermal stresses . The experimental results were compared with the numerical results obtained with a commercial finite element software. For this analysis, some thermal parameters such as the convective heat transfer coefficient, the density, the thermal conductivity and the specific heat were experimentally obtained. In general, a good agreement between experimental and numerical results was observed. The results of this study, together with the results of fatigue and fracture tests, will be used in a tolerance analysis of defects in the products manufactured with these composites.     

A hierarchy of probabilistic system types

We arrange various types of probabilistic transition systems studied in the literature in an expressiveness hierarchy. The expressiveness criterion is the existence of an embedding of systems of the one class into those of the other. An embedding here is a system transformation which preserves and reflects bisimilarity. To facilitate the task, we define the classes of systems and the corresponding notion of bisimilarity coalgebraically and use the new technical result that an embedding arises from a natural transformation with injective components between the two coalgebra functors under consideration. Moreover, we argue that coalgebraic bisimilarity, on which we base our results, coincides with the concrete notions proposed in the literature for the different system classes, exemplified by a detailed proof for the case of general Segala-type systems.     

On-line diagnosis and uncertainty management using evidence theory––experimental illustration to anaerobic digestion processes

The on-line diagnosis is a key requirement in biological processes. This is particularly true in the case of wastewater treatment processes due to the composition of media, the requirements of operating conditions and the wide variety of possible disturbances that necessitate careful and constant monitoring of the processes. Moreover, because only partial information is available in an on-line context and because of the technical and biological complexities of the involved processes, specific characteristics are required for diagnosis purposes. Several approaches like quantitative model based, qualitative model based and process history based methods were applied over the years. This paper present a methodological framework based on evidence theory to manage the fault signals generated by conventional approaches (i.e., residuals from hardware and software redundancies, fuzzy logic based modules for process state assessment) and to account for uncertainty. The advantages of using evidence theory like modularity, detection of conflict and doubt in the information sources are illustrated with experimental results from a 1 m³ fixed bed anaerobic digestion process used for the treatment of industrial distillery wastewater.     

Maize processing waste water arabinoxylans: Gelling capability and cross-linking content

Water-soluble feruloylated arabinoxylans were extracted from maize processing waste water (nejayote) generated from tortilla-making industries. Nejayote arabinoxylans (NAX) presented a ferulic acid content of 0.23 μg/mg, an arabinose to xylose ratio (A/X) of 0.65, an intrinsic viscosity, [η], of 183 ml/g and a molecular weight (Mw) of 60 kDa. Laccase-induced gels were obtained from 4% (w/v) NAX solution while, at lower concentrations, no gelation was observed. Laccase covalent cross-linking of NAX led to the formation of diferulic (di-FA) and triferulic (tri-FA) acid structures. 4% (w/v) NAX gel presented di-FA and tri-FA contents of 0.02 and 0.01 μg/mg NAX, respectively, and a G′ value of 2 Pa. Recuperation of this gum from a low-value maize by-product could represent a commercial advantage over other gums commonly used in the food industry.     

Volatile compounds in Spanish dry-fermented sausage ‘salchichón’ subjected to high pressure processing. Effect of the packaging material

The effect of high pressure treatment (400 MPa, 10 min at 12 °C) on the volatile profile of Spanish dry-fermented sausage ‘salchichón’, packaged with or without aluminium foil in a multilayer polymeric bag, was investigated. The analysis of the volatile fraction was carried out by dynamic headspace extraction coupled to gas chromatography–mass spectrometry. Pressure-treated samples showed significantly higher levels of alcohols, aldehydes and alkanes and lower levels of two methylketones as compared with control samples. An intense migration was observed of compounds from the plastic material into the product, mainly linear and branched-chain alkanes, alkenes and benzene compounds. Most of these migrating compounds were significantly more abundant in pressurized samples than in untreated samples.     

Identification of Aspergillus tubingensis strains responsible for OTA contamination in grapes and wine based on the acyl transferase domain of a polyketide synthase gene

Restriction digestion analysis of the acyl transferase (AT) domain sequences of a polyketide synthase (PKS) gene was tested as a rapid method to identify isolates of Aspergillus tubingensis from grapes. Restriction endonuclease digestion of PKS products using the endonucleases Bcc I, Hae III, Hpa II, Mbo I and Taq I distinguished five types of restriction fragment length polymorphism (RFLP). Ochratoxigenic isolates were only identified within RFLP-types I and III. The RFLP assay is proposed as a rapid and easy method to identify A. tubingensis isolates from grapes. Amino acid sequences of AT domains from representative A. tubingensis isolates of the RFLP types obtained were aligned and analysed using phylogenetic methods. A comparison was also made with reference strains of Aspergillus section Nigri . Most of the A. tubingensis strains clustered into two distinct groups Gr1 and Gr2 with the exception of two isolates that remained unclustered. These results support the intraspeficific variability within A. tubingensis species reported using other techniques.     

Determination of fruit origin by using 26S rDNA fingerprinting of yeast communities by PCR–DGGE: preliminary application to Physalis fruits from Egypt

The determination of geographical origin is a demand of the traceability system of import–export food products. One hypothesis for tracing the source of a product is by global analysis of the microbial communities of the food and statistical linkage of this analysis to the geographical origin of the food. For this purpose, a molecular technique employing 26S rDNA profiles generated by PCR–DGGE was used to detect the variation in yeast community structures of three species of Physalis fruit (Physalis ixocarpa Brat, Physalis pubescens L, Physalis pruinosa L) from four Egyptian regions (Qalyoubia, Minufiya, Beheira and Alexandria Governments). When the 26S rDNA profiles were analysed by multivariate analysis, distinct microbial communities were detected. The band profiles of Physalis yeasts from different Governments were specific for each location and could be used as a bar code to discriminate the origin of the fruits. This method is a new traceability tool which provides fruit products with a unique biological bar code and makes it possible to trace back the fruits to their original location. Copyright © 2009 John Wiley & Sons, Ltd.     

Physico-chemical characterisation of a non-conventional food protein source from earthworms and sensory impact in arepas

This study aimed to characterise a non-conventional protein source: a powder made from earthworms, and to evaluate its potential use as human food. The way it was prepared led to low solubility and wide particle size distribution. Sensory analysis was used to assess the acceptability and the organoleptic properties of maize-based pan-cakes fortified with this novel protein powder. Satisfying products were obtained with a substitution level of 5.5% (w/w) earthworm powder in pan-cakes. GC-MS allowed the identification of more than seventy volatile compounds that may be responsible for the off-odour of the powder. The most abundant chemical groups found in the volatile fraction were ketones with undecan-2-one, alcohols with pentan-1-ol, and aldehydes with hexanal. Partial delipidation was tested as a way to improve the organoleptic quality of the powder. It clearly led to less intensely coloured samples but delipidation must be optimised to have an impact on odour.     

Fatty acid profile changes during orange juice‐milk beverage processing by high‐pulsed electric field

High‐intensity pulsed electric fields (HIPEF) is an emerging non‐thermal food preservation technology which has the potential to pasteurize pumpable liquid foods. Its application is being studied to evaluate it as potential alternative or complementary process to thermal pasteurization. Orange juice‐milk beverage with added bioactive components is a ready‐to‐drink beverage developed as an alternative to traditional soft drinks. In the present work, two HIPEF treatments (35 and 40 kV/cm) and six different treatment times (from 40 to 180 µs) were evaluated to assess their effect on the fatty acid profile of an orange juice‐milk beverage fortified with n‐3 fatty acids and oleic acid. The effect of HIPEF treatment on various physicochemical properties of the beverages: pH, °Brix, hydroxymethylfurfural or peroxide index was also determined. After HIPEF treatment, non‐significant changes in the contents of saturated fatty acids, monounsaturated fatty acids or polyunsaturated fatty acids were observed. Neither peroxides nor intolerable levels of furfurals were detected. Only a small reduction in fat content (p <0.05) was found. In conclusion, HIPEF can be proposed as an alternative preservation technology due to these minimal changes which are negligible from the nutritional point of view.