Modeling of thermal stresses and lifetime prediction of planar solid oxide fuel cell under thermal cycling conditions

A typical operating temperature of a solid oxide fuel cell (SOFC) is above 600 °C, which leads to severe thermal stresses caused by the difference in material mechanical properties during thermal cycling. Interfacial shear stress and peeling stress are the two types of thermal stresses that can cause the mechanical failure of the SOFC. Two commonly used SOFC configurations (electrolyte-supported and anode-supported) were considered for this study. The paper developed a mathematical model to estimate the thermal stresses and to predict the lifetime of the cell (Ni/8YSZ-YSZ-LSM). Due to the mismatch of the material mechanical properties of the cell layers, a crack nucleation induced by thermal stresses can be predicted by the crack damage growth rate and the initial damage distribution in the interfacial layer for each thermal cycle. It was found that the interfacial shear stress and peeling stress were more concentrated near the electrode free edge areas. The number of cycles needed for failure decreased with the increase in the porosity of electrode. The number of cycle for failure decreased with increase in electrolyte thickness for both anode- and electrolyte-supported SOFC. The model provides insight into the distribution of interfacial shear stress and peeling stress and can also predict damage evolution in a localized damage area in different SOFC configurations.     

Physicochemical and Nutritional Characteristics of Organic Acid-Treated Button Mushrooms (Agaricus bisporous)

An effort was made to evaluate the effectiveness of organic acids to improve the quality and shelf life of button mushroom (Agaricus bisporous). Shelf life of malic acid-treated mushrooms was improved to a significant level (p < 0.05) in terms of increased whiteness and texture. Sensorial properties, chemical components, and dietary fibers of treated mushrooms remained unaltered. Antioxidant levels of treated mushrooms to scavenge free radical of 2,2-diphenyl-1-picrylhydrazyl and 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid), polyphenolics content, flavonoids content, and superoxide dismutase activity were not affected. For determining the effectiveness of malic acid as a sanitizer, mushroom slices were artificially inoculated with five foodborne pathogens. Of the pathogens tested, Escherichia coli O15:H7 and Cronobacter sakazakii were inactivated to the maximum; Salmonella typhimurium, Listeria monocytogenes, and Campylobacter jejuni were also reduced significantly (p < 0.05) following storage for up to 5 days at 15°C with 2% and 4% of malic acid. Negligible growth was observed upon storage of treated mushrooms at 4°C. The results of our study suggested malic acid treatment as an economical minimal processing strategy for edible mushrooms.     

Optimization of bending and shear rigidities of woven fabrics using desirability function

Abstract

Banding and shear properties influence the drape and handle characteristics of woven fabrics. As bending and shear rigidities of woven fabrics generally have high degree of association, it is difficult to design a woven fabric having low bending rigidity and high shear rigidity or vice versa. This paper deals with the optimization of bending and shear rigidities of woven fabrics using the desirability function approach. Low stress mechanical properties such as bending rigidity and shear rigidity have been combined to represent ‘the overall desirability’ which is varying from 0 to 1. The overall desirability has been maximized against the target values of shear and bending rigidities. It was possible to attain overall desirability of 0.684 resulting from individual desirability of 0.662 and 0.707 for banding and shear rigidities, respectively. Experimental validation confirms that the applied method can be effectively used to optimize the woven fabric mechanical properties at low stress region.