Electrical contact resistance between stainless steel bipolar plate and carbon felt in PEFC: A comprehensive study

Bipolar plate represents a key component of Proton Exchange Membrane Fuel Cell (PEFC) with several essential functions, among them the electric connection of elementary cells. Usually made of graphite, this component is studied worldwide in order to develop a commercially viable alternative: different ways have been being investigated, and to date, despite corrosion issues, stainless steel (SS) appears as a good candidate material, but its Electrical Contact Resistance (ECR) can reach unacceptable values when exposed to PEFC environment. This paper offers a comprehensive study of the parameters acting on ECR when using uncoated SS in PEFC: roughness, which influences the surface contact area with carbon baking, bulk composition of the alloy, which influences only partly the nature of passive films, and the composition and structure of passive films, strongly modified by surface treatments and ageing conditions.     

The effect of concentrated masses on the response of a plate under a turbulent boundary layer excitation

This work is aimed at the numerical analysis of the vibration response of a plate, carrying one or more concentrated masses, under a stochastic, and convective load. The pressure load is a typical turbulent boundary layer excitation (TBL) and the structural configurations reproduce common experimental situations because the concentrated masses can be considered similar to accelerometer sensors.The models adopt the Corcos TBL model and the concentrated masses are simulated with the Dirac singularity function. The approximations, introduced with the above assumptions on the concentrated masses, and the necessary numerical accuracy, in calculating the structural responses, are discussed.The added masses do not lead to a relevant modification of the global structural response but, on the contrary, the results show that the local effects can be relevant: the paper highlights the differences of the vibration responses from the analogous structural configurations under a stochastic load without convective characteristics.     

Acerola and cashew apple as sources of antioxidants and dietary fibre

Several tropical fruits have been described as natural sources of dietary fibre (DF) and phenolic compounds, associated with different health effects. The aim of this work was to ascertain the DF, phenolic compounds content (including non‐extractable polyphenols, mostly associated with DF) and antioxidant capacity in acerola fruits and cashew apples from selected clones. ‘BRS 236’ acerola fruits presented a high antioxidant capacity because of the combination of both extractable polyphenols and l ‐ascorbic acid (providing together a Folin value of 170 kg^?1 g d.m.). ‘CCP 76’ cashew apples contained 28 g kg^?1 d.m. of extractable polyphenols and 13 g kg^?1 d.m. of ascorbic acid as well as a high amount of non‐extractable condensed tannins (52 g kg^?1 d.m.). DF content was of 260 g kg^?1 d.m. in acerola fruit and of 209 g kg^?1 d.m. in cashew apple. Acerola fruits and cashew apple should therefore be considered as new natural sources of DF and phenolic compounds.     

Design of a Stable DC Voltage Source and Computer Controlling of It Using an Indigenously Developed All-Digital Addressing-Cum-Control Hardware

We have developed a digitally operated addressing and control module (DACM) for addressing and controlling of equipment from a remote computer using a communication protocol developed in-house. This is useful for automation of an experiment that uses multiple equipment in a pre-decided synchronized manner. We also report design of a multipurpose high voltage direct current (DC) source that provides output of 0–100 V with an average stability of 1.90 (36) mV and has minimum step size of 3 mV. Operation of the DACM is examined by selecting the desired equipment, which in this case is the dc source, and remotely controlling its output from a computer. We also show that this can generate voltage with different waveforms within a 0–10 Hz frequency bandwidth. Such computer controlled ultra-stable high voltage sources tuneable to any arbitrary waveforms at low frequencies have many applications such as, driving a piezo for smooth scanning of laser frequencies, tuning length of a Fabry–Perot cavity, biasing of the electrodes in an ion trap and so on.     

Combustion properties of a low-vulnerability propellant: an experimental and theoretical study using laser ignition

Ignition and combustion characteristics of a low-vulnerability propellant based on RDX are studied experimentally. Ignition is obtained using a laser diode. Experiments are performed in a cylindrical closed-volume reactor for different initial pressures and initial propellant masses under nitrogen and argon surrounding atmospheres. Ignition delays, maximal overpressures, and propagation rates are obtained for different initial pressures and laser powers. Thermodynamic predictions of overpressures are also compared with experimental ones. Finally, ignition probabilities for different laser powers and gaseous atmospheres are investigated using a revised Langlie method.     

The genesis and the hydrogeological features of the Turin Po Plain fontanili,typical lowland springs in Northern Italy

The fontanili are typical lowland springs that occur in Northern Italy along the transition zone from high to low plain (the “fontanili line”), due to changes in both the slope surface and the sediment grain size. These resurgences of phreatic water were investigated in the western sector of the Po Plain in the Turin Province. Although the available bibliographic data through 2005 reveal the occurrence of 111 fontanili in the study area, only 51 preserved fontanili have been identified in field surveys. The main morphological and geological features of these resurgences were recorded and entered into a database. In addition, the small-scale hydrogeologic framework of these fontanili was clarified by means of lithostratigraphic cross-sections. Taking into account the drastic decrease in the number of these particular springs, ten fontanili were selected for detailed investigation based on their state of preservation and accessibility. A geological map of each emergence was constructed to explain its origin. The main hydrochemical and physical variables and parameters were measured every month for a period of one year. Only three sources provided water throughout the entire year, and their flow rates reached 60–80 l/S during the summer due to recharge from irrigation channels. All other fontanili remained dry during different periods of the year. The hydrochemical data revealed a Ca–Mg bicarbonate composition. The electrical conductivity increased from the north (100–300 μS/cm) to the south (300–600 μS/cm), and nitrate concentrations were below the limits imposed by Italian law (50 mg/l). This study should be considered as the basis of a proposal to the local government for the protection of a subset of these springs as sites of special geological interest (geo-sites).     

Can the revolution be optimised? Oh yes it can! But,maybe not. Report on the one day symposium on “Varieties of Enactivism”

The “Varieties of Enactivism: A Conceptual Geography” 4th April 2014, was a one day symposium which took place at Goldsmith University, London. The symposium had the explicit aim of clarifying the status of enactive cognitive science both as a unified paradigm for cognitive science and in relation to the broader embodied cognition framework. In what follows I offer a brief summery of the various talks followed by some thoughts on the current state of play within enactivism.     

Deformation mechanism of aluminum–magnesium alloys at elevated temperatures

The study concentrates on the formulation of a reliable constitutive equation for plastic forming of Al–Mg-based alloys above 400 °C and at strain rates above 10^?3 s^?1. The deformation mechanisms of two coarse-grained Al–Mg alloys, also known as AA5182, with grain sizes 21 and 37 μm were investigated. They exhibited optimum extension at 10^?2 s^?1 and at T equal to 425 °C and above 475 °C, respectively, with uniform elongation above 300 %. The strain-rate sensitivity and the stress exponent were equal to 0.25 and 4, respectively, suggesting that the deformation is controlled by the solute drag of gliding dislocations whereas dislocation climb occurs also in grains whose orientation renders them hard. Grain boundary sliding may contribute to a small extent in the deformation process. The threshold stress was found to be small and the activation energy lies between 144 and 136 kJ mol^?1, i.e., that of Al self-diffusion and Mg diffusion in Al. It is concluded that coarse-grained materials may well fulfill the industrial requirements of forming and within this scope, the use of the low purity coarse-grained Al–Mg-based alloys of the AA5182 type would constitute the next step in the course for further cost reduction.     

Identification of quasi-optimal regions in the design space using surrogate modeling

The use of Surrogate Based Optimization (SBO) is widely spread in engineering design to find optimal performance characteristics of expensive simulations (forward analysis: from input to optimal output). However, often the practitioner knows a priori the desired performance and is interested in finding the associated input parameters (reverse analysis: from desired output to input). A popular method to solve such reverse (inverse) problems is to minimize the error between the simulated performance and the desired goal. However, there might be multiple quasi-optimal solutions to the problem. In this paper, the authors propose a novel method to efficiently solve inverse problems and to sample Quasi-Optimal Regions (QORs) in the input (design) space more densely. The development of this technique, based on the probability of improvement criterion and kriging models, is driven by a real-life problem from bio-mechanics, i.e., determining the elasticity of the (rabbit) tympanic membrane, a membrane that converts acoustic sound wave into vibrations of the middle ear ossicular bones.