Fast and exergy efficient start-up of micro-solid oxide fuel cell systems by using the reformer or the post-combustor for start-up heating

The start-up process of a micro-solid oxide fuel cell system strongly influences its overall efficiency, especially for portable applications where a frequent switch-on and switch-off is required. We present herein a novel start-up process for such systems that exploits existing units, such as the post-combustor or the reformer, as a heat source to reach the operation temperature of the cell at 600 °C. Our experimental results show that the employment of platinum catalysts in the post-combustor or rhodium catalysts in the reformer for total oxidation of butane by air combined with an electrically heated wire led to a faster and more efficient start-up than conventional start-up methods using only electrical energy. By using the post-combustor as heat source, the start-up time could be reduced by 79% and the exergy cost by 86%. The latter includes the cost of the stand-alone fuel cell system to produce electrical energy for the joule heating of the wire (i.e. the system efficiency is accounted for). There are several advantages to use the reformer as heat source during start-up, such as prevention of coking of the fuel cell or improved heat transfer by internal heating of the other components. The start-up performance, however, was lower than that of the post-combustor: the start-up time could be reduced by 65% and the exergy cost by 68% compared to a conventional start-up.     

Rapid production of micropatterned surfaces using a fluid dynamical instability

The continuous, high speed patterning of polyethylene films with a micron‐structured silicone coating was investigated in a roll coating process that did not depend on the use of prestructured tools. Thermally curable polydimethylsiloxane (PDMS) resin was rheologically modified by the addition of highly agglomerated, aerosol‐derived silica and resulted in a Herschel–Bulkley fluid. Application of the modified siloxane in a roll coating process resulted in a fluid dynamical instability at high capillary numbers promoting the spontaneous formation of randomly branched surface structures. The shear‐thinning properties of the nanoparticle‐doped PDMS resin were adjusted as to preserve the wet, structured coating during the following thermal curing step. The highly regular pattern was characterized in terms of averaged branch width and could be controlled from micro‐ to millimeter size by adjusting coating roll velocity and roll gap distance. The adhesive properties of the structured coating were compared to unstructured conventional silicone coatings by measuring the release force of pressure‐sensitive adhesives. For rubber‐based tape, the release force of patterned PDMS was reduced by a factor of up to eight if compared to smooth reference silicone. These ultra‐low adhesive coatings may find applications in packaging, food processing, and for covering sanitary surfaces, offering a cost‐effective alternative to conventional surface structuring methods. POLYM. ENG. SCI., 46:1541–1547, 2006. © 2006 Society of Plastics Engineers     

Appropriate critical percentages for the Schmidt and Hunter meta-analysis procedure: Comparative evaluation of Type I error rate and power.

Recent investigations have shown that the Schmidt and Hunter 75% meta-analysis procedure (S&H–75%) does not have adequate control of the Type I error rate. This lack of control has caused two problems: First, the S&H–75% displays an erratic relationship between the likelihood to detect moderators and the number of studies included in the meta-analysis. Second, it has precluded meaningful power comparisons of the S&H–75% procedure with alternate procedures. In the present study we first determine appropriate critical percentages for the Schmidt and Hunter procedure that maintain a fixed Type I error rate. Then we compare this procedure, using the appropriate percentages, with an alternative statistic, U. When the correct percentages are used, the Schmidt and Hunter procedure shows equivalent power to the U statistic. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Micro-organism-triggered release of silver nanoparticles from biodegradable oxide carriers allows preparation of self-sterilizing polymer surfaces

The antimicrobial activity of silver has attracted significant research interest and contributes to an exponentially growing use of this noble metal in commodity products. In this investigation, we describe a general approach to increase the antimicrobial activity of a silver-containing surface by two to three orders of magnitude. The use of 1-2-nm silver particles decorating the surface of 20-50-nm carrier particles consisting of a phosphate-based, biodegradable ceramic allows the triggered release of silver in the presence of a growing microorganism. This effect is based on the organism's requirements for mineral uptake during growth creating a flux of calcium, phosphate, and other ions to the organism. The growing micro-organism dissolves the carrier containing these nutrients and thereby releases the silver nanoparticles. Further, we demonstrate the rapid self-sterilization of polymer surfaces containing silver on calcium phosphate nanoparticles using a series of human pathogens. Colony-forming units (viable bacteria or fungi counts) have been routinely reduced below detection limit and suggest application of these self-sterilizing surfaces in hospital environments, food and pharmaceutical processing, and personal care.     

Neural network modelling of the inductively coupled RF plasma synthesis of silicon nanoparticles

The synthesis of silicon nanopowders by an inductively coupled plasma (ICP) process is investigated. The specific surface area (SSA) of the elaborated particles is determined by nitrogen absorption (BET) as a function of the quenching gas flow rate and the precursor feeding rate. Nanopowders with specific surface areas varying from 69 to 194 m² g^− 1, corresponding to equivalent particle sizes of 37 and 13 nm respectively, could be produced. The correlation between these two input parameters and the output SSA has been numerically modelled with linear regression and artificial neural networks approaches. It has been demonstrated that with the available data set, a regression model with quadratic regressors and a neural network modelling give a similar response.     

A meta-analysis of the relation of job characteristics to job satisfaction.

Determined, using meta-analysis procedures, the relation between job characteristics and job satisfaction in 28 studies. The role of growth need strength (GNS) as a possible moderator of this relation was also investigated. Results indicate a moderate relation between job characteristics and job satisfaction. This relation was stronger for employees high in GNS. It is suggested that situational characteristics were more important in determining satisfaction for employees low in GNS. A model based on these findings is proposed. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Syngas production from butane using a flame-made Rh/Ce0.5Zr0.5O2 catalyst

The capability of flame-made Rh/Ce_0.5Zr_0.5O₂ nanoparticles catalyzing the production of H₂- and CO-rich syngas from butane was investigated for different Rh loadings (0–2.0 wt% Rh) and two different ceramic fibers (Al₂O₃/SiO₂ and SiO₂) as plugging material in a packed bed reactor for a temperature range from 225 to 750 °C. The main goal of this study was the efficient processing of butane at temperatures between 500 and 600 °C for a micro-intermediate-temperature SOFC system. Our results showed that Rh/Ce_0.5Zr_0.5O₂ nanoparticles offer a very promising material for butane-to-syngas conversion with complete butane conversion and a hydrogen yield of 77% at 600 °C. The catalytic performance of packed beds strongly depended on the use of either Al₂O₃/SiO₂ or SiO₂ fiber plugs. This astonishing effect could be attributed to the interplay of homogeneous and heterogeneous chemical reactions during the high-temperatures within the reactor.