High temperature proton exchange membrane fuel cell using a sulfonated membrane obtained via H2SO4 treatment of PEEK-WC

A method for the sulfonation of PEEK-WC, a glassy poly(ether ether ketone) with sulphuric acid is presented. Depending on the reaction time, polymers with ion exchange capacity (IEC) from 0.30 to 0.76 meq_H⁺/g are obtained, as determined by titration with NaOH solutions. The thermal properties of the polymers were studied by differential scanning calorimetry, showing that the glass transition temperature increases with increasing degree of sulfonation, from 224 °C for pure PEEK-WC to 246 °C for the polymer having an IEC of 0.76 meq_H⁺/g. The sulfonated polymers were used to prepare proton exchange membranes for possible application in fuel cells. Dense membranes were prepared by solvent evaporation, using DMA as the solvent. The transport properties of the membranes were determined in terms of water uptake and permeability for hydrogen and oxygen. Electrochemical characterization was performed by measuring cell voltage and power density curves as a function of current density at different working temperatures and the results were compared with those of a commercial Nafion membrane. A power density of 284 mW/cm² was obtained for S-PEEK-WC membrane at 120 °C in H₂/air fuel cell, slightly above the corresponding value found for Nafion.     

Reactivity of Mg-Ba catalyst in NOx storage/reduction

A new catalyst for NO_x storage/reduction was prepared to improve the activity of Ba-Pt/γ-Al₂O₃ by replacing Ba with a mixture of Ba and Mg. The catalyst was prepared by impregnating 1 wt.% Pt and then the alkaline-earth metals (Mg, Ba) on commercial γ-Al₂O₃. The tests have been carried out in a wide temperature range (ca. 200–400 °C) in order to understand the role of the mixture of alkaline-earth metals as a function of temperature. The behaviour of the two catalysts was different and indicated a synergetic effect between Mg and Ba.     

Hydrogen production from methanol by oxidative steam reforming carried out in a membrane reactor

The aim of this work is to study from an experimental point of view the oxidative steam reforming of methanol by investigating the behaviour of a dense Pd/Ag membrane reactor (MR) in terms of methanol conversion as well as hydrogen production. The main parameters considered are the operating temperature and the O₂/CH₃OH feed ratio. This is a pioneer work in the application of MR to this kind of reaction, whose goal should be to produce a CO-free hydrogen stream suitable for hydrogen fuel cell applications. The experimental results show that the MR gives methanol conversions higher than traditional reactors (TRs) at each temperature investigated, confirming the good potential of the membrane reactor device for this interesting reaction system.     

Biosurfactant Production by Pseudomonas aeruginosa and Yarrowia lipolytica and Its Use for Detergent Formulations

This work reports detergents production using biological surfactants, microbiologically synthesized, and compares its foaming power and emulsification capacity to those presented by a petroleum based surfactant. Both used microorganisms were capable to produce surfactants, been able to emulsify oil/water mixtures and cause decrease of surface tension of water. The biosurfactant produced from Yarrowia lipolytica has a critical micelle concentration lower than that obtained from Pseudomonas aeruginosa （10 and 30 mg·Lt, respectively）, but the later showed better results in foaming power and emulsification experiments, similar to the synthetic detergent.     

Effect of silicates on the structure of Ni-containing catalysts obtained from hydrotalcite-type precursors

New nickel hydrotalcite-like compounds with silicates as interlayer anions used as catalyst precursors in the catalytic partial oxidation of methane were prepared by the coprecipitation method. The properties of these materials were compared with those of compounds obtained from carbonate-containing materials. The precursors and calcined samples were characterized by powder X-ray diffraction, FT-IR and Vis/UV/NIR spectroscopies, thermal analyses (DTA and TG), temperature programmed reduction (TPR) and N₂ adsorption/desorption at −196 °C. The results show that the incorporation of silicates in the lamellar compounds modifies the structural and textural properties of the precursors. After calcination, silicates – which are non-volatile anions – contribute to the final structure of the catalysts, which form a new forsterite-like phase, increasing their specific surface area but not altering the reducibility of the nickel species.     

An Optimization Approach to Petri Net Monitor Design

This note addresses the problem of enforcing generalized mutual exclusion constraints on a Petri net plant. First, we replace the classical partition of the event set into controllable and uncontrollable events from supervisory control theory, by associating a control and observation cost to each event. This leads naturally to formulate the supervisory control problem as an optimal control problem. Monitor places which enforce the constraint are devised as a solution of an integer linear programming problem whose objective function is expressed in terms of the introduced costs. Second, we consider timed models for which the monitor choice may lead to performance optimization. If the plant net belongs to the class of mono-T-semiflow nets, we present an integer linear fractional programming approach to synthesize the optimal monitor so as to minimize the cycle time lower bound of the closed loop net. For strongly connected marked graphs the cycle time of the closed-loop net can be minimized     

Coronary artery bypass grafting versus percutaneous coronary intervention in end-stage kidney disease: A systematic review and meta-analysis of clinical studies

The most significant complication of end-stage kidney disease (ESKD) is cardiovascular disease, mainly coronary artery disease (CAD). Although the effective treatment of CAD is an important prognostic factor, whether percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) is better for treating CAD in this group of patients is still controversial. We searched Pubmed/Medline, Web of Science, Embase, the Cochrane Central Register of Controlled Trials articles that compared the outcomes of CABG versus PCI in patients with ESKD requiring dialysis. A total of 10 observational studies with 39,666 patients were included. Our analysis showed that when compared to PCI, CABG had lower risk of need for repeat revascularization (relative risk [RR] = 2.25, 95% confidence interval [CI] 2.1–2.42, p < 0.00001) and cardiovascular death (RR = 1.19, 95% CI 1.14–1.23, p < 0.00001) and higher risk for short-term mortality (RR = 0.43, 95% CI 0.38–0.48, p < 0.00001). There was no statistically significant difference between the PCI and CABG groups in the risk for late mortality (RR = 1.05, 95% CI 0.97–1.14, p = 0.25), myocardial infarction (RR = 1.05, 95% CI 0.46–2.36, p = 0.91) or stroke (RR = 1.02, 95% CI 0.64–1.61, p = 0.95). This meta-analysis showed that in ESKD patients requiring dialysis, CABG was superior to PCI in regard to cardiovascular death and need for repeat revascularization and inferior to PCI in regard to short term mortality. However, this meta-analysis has limitations and needs confirmation with large randomized controlled trials.     

Waves and forms: constructing the cultural in design

While research in HCI on dealing with cultural issues when designing ICTs tended to adopt fixed and taxonomic views, recent theoretical perspectives closer to the social sciences have called for attending to the contingent, fluid, and dynamic aspects of the notion of culture. In this article, we contribute to translating these perspectives into an approach for informing design. We focus on abandoning prior conceptions of culture to allow the discovery of cultural differences through inductive field research while engaging with the target community. This allows a view on cultural difference that is generative for design: it is unique to each case, and it also remains close to the concerns of community members. We base our approach on Basile Zimmermann’s (2015) waves and forms framework, and we illustrate it through our engagement and design with VOCI, a local voluntary community of tech-savvy university students in Syria between 2011 and 2015.

     

Sulla determinazione degli errori nel controllo predittivo dei processi mediante calcolatori

Sommario Si considera il problema della determinazione degli errori nella risposta di un sistema fisico a molte variabili, soggetto ad un controllo di tipo predittivo mediante calcolatore elettronico, dovuti ad imprecisioni nella riproduzione delle funzioni d'ingresso e nella identificazione del modello matematico. Viene quindi illustrata l'applicazione del procedimento al calcolo degli errori da cui è affetto il posizionamento in tempo minimo di un sistema lineare del secondo ordine.

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Summary The analysis of errors wich affect the behavior of a physical multivariable system subject to a predictive control by an ?on line? computer, is considered. The origin of these errors are the non perfect reproduction of the pre-calculated values of the manipulated variables and the imperfect knowledge of the system. An example is worked out, in which the results of the previous analysis are applied in the case of a second order system subject to a time-optimal bang-bang control.