Transfer of Ultrafine Particles and Air in Multi-storey Buildings

An emerging issue in Denmark is passive smoking in residential buildings where non-smokers are exposed to smoke from their neighbours. There are various ways that smoke is transferred from one flat to another. The air transfer rate between two flats in a multi-storey building depends on its construction, tightness and age. This paper presents results of a study on the transfer of ultrafine particles and tracer gas in an older multi-storey building in Copenhagen. The aim of the study was to quantify the transfer ofultrafine particles and gases from one flat to another fiat before and after sealing the floor. A new floor-sealing method was applied to seal the floor between the two flats. The sealing method was developed by a firm specialising in sealing. Indoor ultrafine particle concentrations and tracer gas were measured continuously in the two fiats during the measuring periods. In the unoccupied fiat, the gas source was N20 and the particle source was burning cigarettes. Reduction of the concentration of ultrafine particles and tracer gas by sealing the floor with polyethylene and joint filler made of bitumen was studied. It was evaluated how the sealing performed with regard to decreasing the amount of ultrafine particles and a tracer gas transferred between two fiats separated by a floor. When the floor between the flats was not sealed, the results showed that about 4% of the ultraflne particles and 14% of the tracer gas were transferred. After sealing, the amount transferred was reduced to 1.6% and 5%, respectively.     

Fabrication of Fischer–Tropsch Catalysts by Deposition of Iron Nanocrystals on Carbon Nanotubes

The fabrication of supported catalysts consisting of colloidal iron oxide nanocrystals with tunable size, geometry, and loading—homogeneously dispersed on carbon nanotube (CNT) supports—is described herein. The catalyst synthesis is performed in a two‐step approach. First, colloidal iron and iron oxide nanocrystals with a narrow size distribution are produced. Second, the nanocrystals are attached to CNT grains serving as support structure. Important features, like iron loading and nanocrystal density on the CNT support, are controlled by changing the nanocrystal concentration and ligand concentration, respectively. The Fischer–Tropsch performance reveals these new materials to be active, selective toward lower olefins (60% C of hydrocarbons produced in the absence of promoters), and remarkably stable against particle growth.     

Preparation and operation of gas diffusion electrodes for high-temperature proton exchange membrane fuel cells

Gas diffusion electrodes for high-temperature PEMFC based on acid-doped polybenzimidazole membranes were prepared by a tape-casting method. The overall porosity of the electrodes was tailored in a range from 38% to 59% by introducing porogens into the supporting and/or catalyst layers. The investigated porogens include volatile ammonium oxalate, carbonate and acetate and acid-soluble zinc oxide, among which are ammonium oxalate and ZnO more effective in improving the overall electrode porosity. Effects of the electrode porosity on the fuel cell performance were investigated in terms of the cathodic limiting current density and minimum air stoichiometry, anodic limiting current and hydrogen utilization, as well as operations under different pressures and temperatures.     

Energy and environment : Nordic energy scenarios for 2010 and 2030

The concept of a sustainable energy sector has received wide attention since the publication of the Brundtland Report in 1987. This paper analyses the possibilities of establishing by 2010 and 2030 an energy system in the Nordic countries which prevents the critical loads of NO_x and SO₂ respectively on the most vulnerable Nordic ecological systems being exceeded. In addition, the present concentration of CO₂ in the atmosphere should not be significantly exceeded within a time horizon to around 2050. Different scenarios have been investigated in order to analyse the scope for attaining such a sustainable energy development within the limits of existing technologies and known potentials of renewable energy sources. Data on the technologies are available in a special catalogue.     

Making carbon nanotube electron sources of defined lengths and with closed caps

A method is reported to make an electron source consisting of an individual multi-walled carbon nanotube (MWNT) mounted on a tungsten support tip, and cut to length using localized electron beam irradiation in a scanning electron microscope. The apex of the MWNT was transformed into a closed cap with at least one fullerene-like layer via an annealing process involving simultaneous heating and the extraction of an emission current of ～ 1 mA. The electron emission occurred at localized emission sites. The electron emission showed Fowler-Nordheim behavior, was highly stable with time, and exhibited a low energy spread. The structure of the caps of two MWNTs was studied with transmission electron microscopy before and after the cap closure.     

Aerodynamic structures and processes in rotationally augmented flow fields

Rotational augmentation of horizontal axis wind turbine blade aerodynamics currently remains incompletely characterized and understood. To address this, the present study concurrently analysed experimental measurements and computational predictions, both of which were unique and of high quality. Experimental measurements consisted of surface pressure data statistics used to infer sectional boundary layer state and to quantify normal force levels. Computed predictions included high‐resolution boundary layer topologies and detailed above‐surface flow field structures. This synergy was exploited to reliably identify and track pertinent features in the rotating blade boundary layer topology as they evolved in response to varying wind speed. Subsequently, boundary layer state was linked to above‐surface flow field structure and used to deduce mechanisms underlying augmented aerodynamic force production during rotating conditions. Copyright © 2007 John Wiley &Sons, Ltd.     

Why Au and Cu Are More Selective Than Pt for Preferential Oxidation of CO at Low Temperature

Self-consistent, periodic density functional theory (DFT) calculations and micro-kinetic modeling are used to compare selectivity for the preferential oxidation of CO (PROX) with respect to H₂ based on studies of elementary reaction steps on the (111) facet of Au, Cu and Pt. The first step of H oxidation (OH formation) has a higher activation barrier than the second step (H₂O formation) on all three metal surfaces, indicating that OH formation competes with CO oxidation for the removal of trace amounts of CO from a typical reformate gas. The activation energy barrier for CO oxidation is found to be 0.18eV on Au(111), 0.82eV on Cu(111) and 0.96eV on Pt(111), whereas the barrier for OH formation is 0.90, 1.28 and 0.83eV respectively. A micro-kinetic model based on the DFT results shows that trends in the selectivity of these metals at different temperatures is due to (i) differences in the rate constants of the competitive CO and H oxidation reactions, and (ii) differences in the CO and H surface coverages. Our results explain why Au and Cu are more selective PROX catalysts compared to Pt at low temperatures. At higher temperatures, Pt and Cu lose some of their selectivity to CO oxidation, whereas the selectivity on Au decreases substantially primarily because of the significantly weaker CO adsorption.     

Combining remote sensing and anthropology to trace historical land-use changes and facilitate better landscape management in a sub-watershed in North Thailand

A research project intended to extract the history of land-use in a sub-watershed in Thailand by combining remote sensing and anthropology ended up providing local villagers with a useful tool for developing a more sustainable landscape management. In three villages people were interviewed in-depth about historical land-use changes and they helped to make land-use maps approximately covering the years 1973, 1980, 1989, and 1999. These maps were digitized and compared to satellite images from the same years. Trends and discrepancies between the two sets of maps were then analysed and discussed with the villagers in order to establish the local land-use history. The involvement of local groups in the mapping process was instrumental in overcoming long-standing inter-village conflicts, mainly by creating a common knowledge platform on which co-management could be based. The research helped set in motion a process of inter-village forest management cooperation, which was subsequently enhanced by the involvement of CARE Thailand and the local sub-district administration.