Investigation of electrocatalytic activity on a N-doped reduced graphene oxide surface for the oxygen reduction reaction in an alkaline medium

Today the search for new energy resources is a crucial topic for materials science. The development of new effective catalysts for the oxygen reduction reaction can significantly improve the performance of fuel cells as well as electrocatalytic hydrogen production. This study presents the scalable synthesis of nitrogen-doped graphene oxide for the oxygen reduction reaction. The combination of an ab initio theoretical investigation of the oxygen reduction reaction (ORR) mechanism and detailed electrochemical characterization allowed the identification of electrocatalytically active nitrogen functionalities. The dominant effect on electrocatalytic activity is the presence of graphitic and pyridinic nitrogen and also N-oxide functionalities. The overpotential of ORR for nitrogen-doped graphene oxide prepared by microwave-assisted synthesis outperformed the metal-doped graphene materials.     

Laser Clad and HVOF-Sprayed Stellite 6 Coating in Chlorine-Rich Environment with KCl at 700 °C

Laser clads and HVOF coatings from a stellite 6 alloy (Co–Cr–W–C alloy) on 304 stainless steel substrates were exposed both bare and with KCl deposits in 500 ppm HCl with 5% O₂ for 250 h at 700 °C. SEM/EDX and PXRD analyses with Rietveld refinement were used for assessment of the attack and for analysis of the scales. The bare samples suffered from scale spallation and the scale was mostly composed of Cr₂O₃, CoCr₂O₄ and CoO, although due to dilution haematite (Fe₂O₃) was detected in the scale formed on the laser clad sample. A small amount of hydrated HCl was detected in bare samples. While the corrosion of the bare surfaces was limited to comparatively shallow depths and manifested by η and M₇C₃ carbide formation, the presence of KCl on the surface led to severe Cr depletion from the HVOF coating (to 1 wt%). Both inward and outward diffusion of elements occurred in the HVOF coating resulting in Kirdendall voids at the coating–steel interface. The laser clad sample performed significantly better in conditions of the KCl-deposit-induced corrosion. In addition to the oxides, CoCl₂ was detected in the HVOF sample and K₃CrO₄ was detected in the laser clad sample. Thermodynamic calculations and kinetic simulations were carried out to interpret the oxidation and diffusion behaviours of coatings.     

Olefin production through pyrolysis of triacylglycerols

Triacylglycerols (in Europe particularly rapeseed oil) are the favoured raw materials for production of methyl esters to be used as biodiesel. Another possibility is pyrolysis of triacyglycerols to low molecular weight alkenes and other hydrocarbons. During thermal decomposition under conditions matching those of gas‐oil steam cracking (short residence time, temperature over 800°C) we found the same compounds (mainly ethylene and propylene) as those from classic mineral oil fraction pyrolysis.     

Recognition of business risks when purchasing goods on the Internet using GIS: experience from Slovakia

For operators of Internet shops and their investors on the one hand, and suppliers on the other hand, knowledge of the consumer market is becoming critical in terms of the risk of non-payment for purchased goods, as most small e-shops maintain their stocks according to current demand. The aim of this paper is to identify customers who come from different districts of Slovakia and display a certain type of consumer behavior regarding the risk connected with willingness to pay for goods purchased via the Internet. To solve this problem we used data from a specialized e-retailer and Geographic Information Systems (GIS) as a Decision Support System generator for constructing maps of consumers to investigate the operation of an e-shop. In the article, we used data from the years 2012–2015 concerning 489 buyers, including their addresses and other geographical data about the consumers and their purchases, and integrated them into the GIS environment. Subsequently, the data were analyzed and documented by means of GIS and maps of consumers were generated. The result of this study is to show that GIS can play a significant role in the decision-making process of e-shops in support of a manager’s experience. The geographical results were evaluated statistically in order to offer a better information capability.     

Artificial intelligence as a discursive practice: the case of embodied software agent systems

In this paper, I explore some of the ways in which Artificial Intelligence (AI) is mediated discursively. I assume that AI is informed by an “ancestral dream” to reproduce nature by artificial means. This dream drives the production of “cyborg discourse”, which hinges on the belief that human nature (especially intelligence) can be reduced to symbol manipulation and hence replicated in a machine. Cyborg discourse, I suggest, produces AI systems by rhetorical means; it does not merely describe AI systems or reflect a set of prevailing attitudes about technology. To support this argument, I analyse a set of research articles about an “embodied conversational agent” called the Real Estate Agent (REA). The articles about REA mobilise a set of rhetorical strategies that systematically downplay the system’s artificiality and bolster its humanlike qualities. Within the context of the dream of AI to produce humanlike machines, and given our strong bias for human-human interaction, the designers’ claim to REA’s humanness in their research articles, as I argue in the final section of this paper, needs little justification.     

Born unwanted: Observations from the Prague Study.

The authors followed 220 children born in 1961-1963 to women twice denied abortion for the same pregnancy in Prague (Czech Republic) and 220 pair-matched controls, whose mothers were pair-matched for age and socioeconomic status and the partner's presence in the home. They were medically, psychologically, and socially assessed in ages 9, 14-16, 21-23, 30, and 35. Although differences between the unwanted study participants and pair-matched controls were not dramatic and changed over time, the differences were consistently in disfavor of the unwanted pregnancy participants. When siblings were used as controls, the findings supported the hypothesis that being born from an unwanted pregnancy is a risk factor for poor mental health in adulthood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A tabu search heuristic for the single vehicle pickup and delivery problem with time windows

The single vehicle pickup and delivery problem with time windows is a generalization of the traveling salesman problem. In such a problem, a number of transportation requests have to be satisfied by one vehicle, each request having constraints to respect: a pickup at its origin and a delivery at its destination, and a time window at each location. The capacity of the vehicle has to be respected. The aim is to minimize the total distance traveled by the vehicle. A number of exact and approximate solution methods exists in the literature, but to the authors knowledge none of them make use of metaheuristics, still promising with other vehicle routing problems. In this paper we present tabu search and probabilistic tabu search. Results obtained on classical traveling salesman problems and a class of randomly generated instances indicate that our approach often produces optimal solutions in a relatively short execution time.     

Improved prediction model for time-dependent deformations of concrete: Part 3-Creep at drying

Part 3 of the present series gives the prediction formulae for the average compliance function in the cross-section of a specimen exposed to drying at constant temperature. The formulae describe the additional creep due to drying by means of the shrinkage function, which automatically introduces the consequences of diffusion theory, such as the dependence of creep on cross-section thickness and shape. The prediction formulae are compared with 19 different data sets from the literature, which reveal relatively good agreement, better than that with previous models. The main source of error is insufficient knowledge of the effect of mix composition and concrete strength. It is advisable to avoid this error by carrying out short-time measurements whenever possible.

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Resume Dans le troisième volet de cette série, on présente les formules de prédiction pour la fonction de compliance moyenne dans la section transversale d’une éprouvette soumise au séchage à température constante. Les formules décrivent le fluage additionnel causé par le séchage au moyen de la fonction de retrait qui introduit automatiquement les aboutissements de la théorie de diffusion, tels ceux qui font dépendre le fluage de l’épaisseur et de la forme de la section transversale. On compare les formules de prédiction à 19 séries de données prises dans la littérature, qui présentent une assez bonne concordance, supérieure à celle obtenue avec les modèles précédents. La source principale d’erreur réside dans une connaissance insuffisante du dosage et de la résistance du béton. On conseille d’éviter cette erreur en effectuant des mesures à court terme chaque fois que c’est possible.

     

Cation exchange kinetics on carboxylic acid resins in a multicomponent system H-Me+Me2+

The exchange kinetics in systems where a carboxylic cation exchange resin in the free acid form comes into contact with solutions, containing Na⁺, Mg²⁺, Ca²⁺, HCO^?₃ and SO^2?₄ have been followed by a shallow bed technique.The relations between the sorption rates of univalent and bivalent cations as well as kinetics of competitive exchange in a ternary system $\text{H}\text{-}$Na⁺Mg²⁺ were studied at low solution concentrations. The effect of polymer matrix crosslinking is studied. The behavior of sulfonic acid resin under the same conditions is given for comparison. The results are discussed in terms of different degrees of selectivities and degrees of dissociation of the carboxylic and sulfonic functional groups.