Characterization and catalytic activity of soft-templated NiO-CeO2 mixed oxides for CO and CO2 co-methanation

Nanosized NiO,CeO₂ and NiO-CeO₂ mixed oxides with different Ni/Ce molar ratios were prepared by the soft template method.All the samples were characterized by different techniques as to their chemical composition,structure,morphology and texture.On the catalysts submitted to the same reduction pretreatment adopted for the activity tests the surface basic properties and specific metal surface area were also determined.NiO and CeO₂ nanocrystals of about 4 nm in size were obtained,regardless of the Ni/Ce molar ratio.The Raman and X-ray photoelectron spectroscopy results proved the formation of defective sites at the NiO-CeO₂ interface,where Ni species are in strong interaction with the support.The microcalorimetric and Fourier transform infrared analyses of the reduced samples highlighted that,unlike metallic nickel,CeO₂ is able to effectively adsorb CO₂,forming carbonates and hydrogen carbonates.After reduction in H2 at 400°C for 1 h,the catalytic performance was studied in the CO and CO₂ co-methanation reaction.Catalytic tests were performed at atmospheric pressure and 300°C,using CO/CO₂/H₂ molar compositions of 1/1/7 or 1/1/5,and space velocities equal to 72000 or 450000 cm³?h^-1?gcat^-1.Whereas CO was almost completely hydrogenated in any investigated experimental conditions,CO₂ conversion was strongly affected by both the CO/CO₂/H₂ ratio and the space velocity.The faster and definitely preferred CO hydrogenation was explained in the light of the different mechanisms of CO and CO₂ methanation.On a selected sample,the influence of the reaction temperature and of a higher number of space velocity values,as well as the stability,were also studied.Provided that the Ni content is optimized,the NiCe system investigated was very promising,being highly active for the CO_x co-methanation reaction in a wide range of operating conditions and stable(up to 50 h)also when submitted to thermal stress.     

Simulations for dynamics of granular mixtures in a rotating drum

We present a simple model and carry out simulations to investigate the dynamics of mixtures of granular material within a rotating drum. On the basis of the commonly held belief (supported by considerable experimental evidence) that segregation is due to motion of particles on the active layer, the bulk playing little or no role, we introduce a 2d lattice gas model which takes into account the rotational frequency, frictional forces, and the gravitational field, and represents segregation tendencies via activated effective grain-grain interactions. Our results include the onset of segregation perpendicular to the drum axis, the appearance and subsequent coarsening of bands and peculiarities of the effects of periodic modulation of the drum. Observed effects such as the segregation of rougher (smoother) particles into the bellies (necks) of the modulation are reproduced by our simulation. Received: 30 March 2000     

Developing Superplastic Ductilities in Ultrafine-Grained Metals

Conventional superplasticity is generally achieved in metals having grain sizes in the range of ∼2 to 5 μm, but processing by equal-channel angular pressing (ECAP) provides the opportunity of introducing exceptional grain refinement and producing materials with ultrafine grain sizes in the submicrometer range. These materials have the potential for exhibiting excellent superplastic properties when tested in tension at elevated temperatures and examples are presented for representative aluminum and magnesium alloys. When these ultrafine-grained materials deform in superplasticity, internal cavities develop as in conventional superplastic alloys. An example is presented for an aluminum-based alloy, and it is shown that the cavity growth processes are also similar to those in conventional alloys. This article is based on a presentation made in the symposium entitled “Ultrafine-Grained Materials: From Basics to Application”, which occurred September 25–27, 2006, in Kloster Irsee, Germany.     

Large-area self-catalysed and selective growth of ZnO nanowires

A simple procedure to selectively grow zinc oxide nanowires (ZnO NWs) on a large scale without any catalyst is reported. The process is based on the use of a zinc metal layer deposited onto substrates before the NW growth. The zinc layer, which becomes liquid at the synthesis temperature, favours the correct local conditions for a selective growth of pure ZnO NWs in an effective area of several square centimetres (up to 20?cm(2) in our laboratory-scale reactor). The?proposed method is suitable for patterned ZnO NW synthesis.     

Implicit–explicit numerical schemes for jump–diffusion processes

Abstract We study the numerical approximation of solutions for parabolic integro-differential equations (PIDE). Similar models arise in option pricing, to generalize the Black–Scholes equation, when the processes which generate the underlying stock returns may contain both a continuous part and jumps. Due to the non-local nature of the integral term, unconditionally stable implicit difference schemes are not practically feasible. Here we propose using implicit-explicit (IMEX) Runge-Kutta methods for the time integration to solve the integral term explicitly, giving higher-order accuracy schemes under weak stability time-step restrictions. Numerical tests are presented to show the computational efficiency of the approximation. Mathematics Subject Classification (1991): Primary: 65M12; Secondary: 35K55, 49L25     

Integrating services and tools in an ICT platform to support eco-innovation in SMEs

Small and medium-sized enterprises (SMEs) represent a key vector to introduce and diffuse eco-innovation in the market, because of their relevance to both the environment and the European gross domestic product. As they are often focused on continuous and incremental innovation of their products, the optimization of product eco-innovation paths can be considered a central aspect of their business. All phases of this process (awareness building and training, analysis, product (re)design and communication/certification) need to be supported to overcome the existing barriers, which mainly consist of lack of experience inside SMEs and cost of information, data, and tools. Information and Communication Technologies can play a role to lower some of the barriers, but currently the numerous services and tools available cover only specific aspects of the whole process, and are often too complex for their direct use by SMEs. The multilingual web-based platform Ecosmes.net here presented aims to integrate user-friendly and free-of-charge services and tools to support all phases of the product eco-innovation process in SMEs. The approach behind mainly consists in developing tailored, simplified tools, and in carrying out ??homogeneous product group?? studies, as a basis for the production of pre-elaborated information and data to be used with the tools developed. Experience gained in 5?years of applications has confirmed that Ecosmes.net can facilitate the start-up of the product eco-innovation process, but has also shown that not all the potentialities have been fully exploited. Moreover, as the eco-innovation market is not developed enough to allow economic management of these kinds of online services, a public initiative is advocated to face this challenge and support a continuous upgrading. Modes and opportunities are proposed and discussed in the conclusion.     

EDIPS: an Easy to Deploy Indoor Positioning System to support loosely coupled mobile work

Loosely coupled mobile work is characterized by nomadic workers collaborating in sporadically and on-demand ways. Supporting nomadic workers’ interactions requires knowing the location of the potential collaborator; therefore, indoor/outdoor positioning systems play a key role. Locating persons in outdoor environments is well addressed by Global Positioning Systems (GPS); however, for the indoor scenario, the solution is not so clear. Although several proposals for indoor positioning have been reported in the literature, most of them demand important setup efforts. This article presents the Easy to Deploy Indoor Positioning System (EDIPS), a WiFi-based system able to support the typical location requirements involved in loosely coupled mobile work. EDIPS is aimed for fast deployment and real-time operations rather than for location accuracy. The system was preliminary evaluated as a support for locating medical interns’ in a simulated hospital. The results obtained indicate the solution is able to locate nomadic workers in an indoor scenario, with enough accuracy to support loosely coupled mobile work, while requiring minimal setup effort.