Au/Pt nanoparticle systems in methanol and carbon monoxide electroxidation

Different Au/Pt bimetallic systems have been synthesised by following the approach suggested by Brust. The nanoparticles have been anchored to glassy carbon surface through a place-exchange reaction involving dithiol molecules. The resulting modified electrode consists of heterogeneous nanostructured Au and Pt patchwork. The different nanoparticles systems developed have been employed for the electroxidation of methanol and carbon monoxide in alkaline aqueous media. The results show that the electrocatalytic activity of the bimetallic systems is enhanced with respect to the single monometallic NP systems.     

Life cycle assessment in buildings: The ENSLIC simplified method and guidelines

Life Cycle Assessment (LCA) is currently used to a very limited extent in the building sector, for several reasons. Firstly, making an LCA evaluation of a building demands a specific tool to handle the large dataset needed and this tool has to be adaptable to the different decisions taken throughout the life cycle of the building. Such tools have been developed in a few countries, but they are exceptions. However, useful experience has been gained in these countries, providing a valuable source of data for developing guidelines for application in other countries. Since the results of a building LCA may contain complex information, the great challenge is to devise efficient ways for communication of the results to users and clients.The simplified methodology presented in this paper adopt a systematic approach guiding the user through the Life Cycle process and clarifying key issues that usually cause difficulty, e.g. choice of assessment tool, definition of system boundaries, options for simplifying the process, etc. The guidelines were developed within the framework of the ENSLIC Building Project, which was co-funded by the European Commission Intelligent Energy for Europe Programme and by nine European organisations that included more than 15 LCA experts and architects.     

Syngas suitability for solid oxide fuel cells applications produced via biomass steam gasification process: Experimental and modeling analysis

The technologies and the processes for the use of biomass as an energy source are not always environmental friendly. It is worth to develop approaches aimed at a more sustainable exploitation of biomass, avoiding whenever possible direct combustion and rather pursuing fuel upgrade paths, also considering direct conversion to electricity through fuel cells. In this context, it is of particular interest the development of the biomass gasification technology for synthesis gas (i.e., syngas) production, and the utilization of the obtained gas in fuel cells systems, in order to generate energy from renewable resources. Among the different kind of fuel cells, SOFCs (solid oxide fuel cells), which can be fed with different type of fuels, seem to be also suitable for this type of gaseous fuel. In this work, the syngas composition produced by means of a continuous biomass steam gasifier (fixed bed) has been characterized. The hydrogen concentration in the syngas is around 60%. The system is equipped with a catalytic filter for syngas purification and some preliminary tests coupling the system with a SOFCs stack are shown. The data on the syngas composition and temperature profile measured during the experimental activity have been used to calibrate a 2-dimensional thermodynamic equilibrium model.     

A staggered grid arrangement for solving incompressible flows with hybrid unstructured meshes

This work presents an alternative to the discretization of the Navier–Stokes equations using a finite volume method for hybrid unstructured grids with a staggered grid arrangement of variables. It has developed a numerical scheme, analogous to the element-based finite volume method, for the solution of 2-D incompressible fluid flow problems using several coupling strategies. All velocity components are stored at each face of the elements (pressure control volumes), following the usual procedure of staggering velocity and pressure. With this staggered arrangement, the balance of mass and momentum is satisfied, simultaneously, for the same set of variables, rendering numerical stability when compared to the nonstaggered arrangement.     

Bridged polysilsequioxane adsorption materials containing phosphonic acid residues

Reactions of hydrolytic polycondensation of bis(triethoxysilane) [(C₂H₅O)₃Si]₂C₂H₄ (or [(C₂H₅O)₃Si]₂C₆H₄) and functional agent (C₂H₅O)₃Si(CH₂)₂P(O)(OC₂H₅)₂ (alkoxysilanes molar ratio of 2: 1 and 4: 1, fluoride ion catalyst and ethanol solvent) yielded powder-like xerogels that contained phosphonic acid residues in the surface layer. Their treatment with boiling concentrated hydrochloric acid resulted in transformation of functional groups ≡Si(CH₂)₂P(O)(OC₂H₅)₂ into acid groups ≡Si(CH₂)₂P(O)(OH)₂. The methods of IR, ¹H MAS NMRm and ¹³C, ²⁹Si, ³¹P MAS NMR spectroscopy showed the following (1) The surface layer in the initial xerogels contains not only phosphorus functional groups, but also some non-hydrolyzed ethoxysilyl groups as well as silanol groups. (2) The hydrochloric acid treatment of the initial xerogels causes the hydrolysis of not only ethoxy groups in the phosphonic acid residues, but also most residual ethoxysilyl groups. (3) Vacuum drying of xerogels after acid treatment forms ≡Si(CH₂)₂P(O)(OH)-OSi≡ links in their surface layer (not more than 20% of phosphorus-containing groups). (4) According to ²⁹Si CP MAS NMR spectroscopic data, boiling acid treatment relatively enriches the xerogel structure T² and T³ units and accounts for the higher rigidity of the hybrid framework. These units also account for retention of the porous structure in these xerogels over time, while most initial xerogels have porous structures that collapse in 12–18 months of storage. The acid-treated xerogels were attributed to microporous adsorbents (having specific surface area of 620 to 760 m²/g). According to the AFM data, both initial and acid-treated xerogels contain almost spherical aggregates of the primary particles (globules).     

Analysis of electricity bills using visual continuous maps

The information from the electricity bills of an institution such as the University of León, with several billing points, constitutes a high-dimensional data set which is quite complicated to visualize at a glance. The use of techniques for dimensionality reduction enables to obtain a two-dimensional representation of the original data set which highlights main features in data and is easier to visualize. If these techniques are combined with interpolation methods, the resulting continuous maps allow comparison and interpretation of a whole range of possible electric data sets, not only the original one. These tools allow us to generate interactive maps that can be used by untrained people to exploit and analyze the information in electricity bills, detect penalties due to a power demand excess or power factor decrease, and make decisions with regard to electricity contracts.     

EFFECT OF HEATED WALL POSITION ON MIXED CONVECTION IN A CHANNEL WITH AN OPEN CAVITY

Mixed convection in an open cavity with a heated wall bounded by a horizontally insulated plate is studied numerically. Three basic heating modes are considered: (a) the heated wall is on the inflow side (assisting flow); (b) the heated wall is on the outflow side (opposing flow); and (c) the heated wall is the horizontal surface of the cavity (heating from below). Mixed convection fluid flow and heat transfer within the cavity is governed by the buoyancy parameter, Richardson number (Ri), and Reynolds number (Re). The results are reported in terms of streamlines, isotherms, wall temperature, and the velocity profiles in the cavity for Ri=0.1 and 100, Re=100 and 1000, and the ratio between the channel and cavity heights (H/D) is in the range 0.1-1.5. The present results show that the maximum temperature values decrease as the Reynolds and the Richardson numbers increase. The effect of the H/D ratio is found to play a significant role on streamline and isotherm patterns for differentheating configurations. The present investigation shows that the opposing forced flow configuration has the highest thermal performance in terms of both maximum temperature and average Nusselt number.     

The determination of total SO2 in grape juice. A comparison among five methods

The EC official method of total SO₂ analysis in grape juice was modified in 1990. The main improvements concerned the amount and concentration of H₃PO₄ used during the distillation to recover the combined SO₂ and the standardization of the distillation time at 15min. This comparative study evaluated the total SO₂ level of 12 grape juices determined by five methods, including distillation, iodimetric and enzymatic-based methods. Attention was focused on the total SO₂ legal limit of 10mg/l fixed in Europe for grape juice. Analysis of variance disclosed a significant difference among the total SO₂ content in grape juices determined by five methods. Each analytical method showed limits in relation of their ability to release the combined SO₂. In particular, the SO₂ bonded to phenolic compounds is partially released at low pH in the acidified juice leading to higher results.     

Counting pedestrians with a zenithal arrangement of depth cameras

Counting people is a basic operation in applications that include surveillance, marketing, services, and others. Recently, computer vision techniques have emerged as a non-intrusive, cost-effective, and reliable solution to the problem of counting pedestrians. In this article, we introduce a system capable of counting people using a cooperating network of depth cameras placed in zenithal position. In our method, we first detect people in each camera of the array separately. Then, we construct and consolidate tracklets based on their closeness and time stamp. Our experimental results show that the method permits to extend the narrow range of a single sensor to wider scenarios.