Surface modifications of gasketless carbon composite bipolar plates for gas tightness of PEM fuel cells

A carbon fiber composite gasketless bipolar plate for proton exchange membrane (PEM) fuel cells was developed using the groove of a trapezoidal shape, which develops large contact stresses due to a wedge mechanism. The surface of the composite groove was modified to increase gas tightness without using rubber gaskets. Graphite, polyimide (PI) and polyethylene terephthalate (PET) film were co-cure bonded on the surface of the bipolar plate during the compression molding process to change its surface hardness, which could affect the gas tightness. Additionally, plasma surface treatment and mechanical abrasion were used to modify the surface morphologies. Corrosion and gas tightness tests on the surface modified bipolar plates were performed to verify the reliability of the gasketless sealing method.     

Mechanical properties of organically modified silicates for bone regeneration

In this paper, different organic–inorganic hybrid materials based in the CaO–SiO₂–poly(dimethyl siloxane) PDMS system have been characterised by means of nanoindentation and their static mechanical properties (Young’s modulus, and hardness) have been investigated. These mechanical properties have been discussed in relation to the chemical composition and structure of the different hybrid materials. Besides, the mechanical behaviour of hybrid materials is visco-elastic and it therefore presents phenomena of creep that will be influenced by the temperature of the mechanical test; undoubtedly, a temperature of 37°C accelerates the processes of creep.     

Dweb model: Representing Web 2.0 dynamism

Due to the increase in the number and popularity of applications such as e-commerce or on-line booking systems, typical of the Web 2.0, dynamic contents are becoming more and more frequent. This trend suggests the review of widely accepted paradigms and models for the World Wide Web. As a system that is continuously changing, both in the offered applications and in its infrastructure, performance evaluation studies are a main concern to provide sound proposals when designing new web-related systems. Although the dynamism in the workload characterization has also been tackled in previous research, it has not been modeled in a precise way yet because of its complex nature.In this paper we propose the Dweb model which represents the dynamism of current web applications in the workload characterization. Dweb is based on three main concepts that allow to model dynamic workload: navigation, workload test and workload distribution. In addition, a dynamic workload generator has been implemented to show the practical application of the proposed model, which has been illustrated through a case study.     

Influence of partial dealcoholization by reverse osmosis on red wine composition and sensory characteristics

Two red wines with a very high ethanol content were partially dealcoholized by reverse osmosis, so that the influence of this technique on wine color, chemical composition and sensory quality could be studied. No statistically significant differences were found in pH, color intensity, total phenolic index, proanthocyanidin concentration and their mean degree of polymerization between control wines and partially dealcoholized wines (?1 and ?2 vol. %). Some slight but significant differences were found in titratable acidity, anthocyanins, CIELab coordinates and polysaccharides. However, these differences were really quite small and only significant in a few cases. Moreover, a trained panel of tasters had severe difficulty in distinguishing between control and partially dealcoholized wines in triangular tests, and results were statistically significant only in some of the comparisons. It is concluded that this technique can be very useful for the partial dealcoholization of red wines because they hardly alter their composition and sensory characteristics.