Domain decomposition improvement of quark propagator estimation

Applying domain decomposition to the lattice Dirac operator and the associated quark propagator, we arrive at expressions which, with the proper insertion of random sources therein, can provide improvement to the estimation of the propagator. Schemes are presented for both open and closed (or loop) propagators. In the end, our technique for improving open contributions is similar to the “maximal variance reduction” approach of Michael and Peisa, but contains the advantage, especially for improved actions, of dealing directly with the Dirac operator. Using these improved open propagators for the Chirally Improved operator, we present preliminary results for the static-light meson spectrum. The improvement of closed propagators is modest: on some configurations there are signs of significant noise reduction of disconnected correlators; on others, the improvement amounts to a smoothening of the same correlators.     

Integration of carbon nanotubes with controllable inclination angle into microsystems

The possibility of growing carbon nanotubes in the immediate proximity of microstructures on a surface in a controllable way, with a high degree of control over the inclination angle, is demonstrated. Carbon nanotubes synthesised in a plasma-enhanced chemical vapour deposition process are known to grow in the direction of the electrical field. Geometrical features of the conductive substrate holder are used to distort the electrical field, thereby controlling the inclination angle of the carbon nanotubes locally. It is shown that the geometrical features of the microstructures on the silicon wafer do not interfere substantially with the resulting inclination angle. Finite element simulations show good agreement with the experimental observations, thus this is a route towards integrating carbon nanotubes with a special inclination angle on microstructures.     

Covariation neglect among novice investors.

In 4 experiments, undergraduates made hypothetical investment choices. In Experiment 1, participants paid more attention to the volatility of individual assets than to the volatility of aggregated portfolios. The results of Experiment 2 show that most participants diversified even when this increased risk because of covariation between the returns of individual assets. In Experiment 3, nearly half of those who seemingly attempted to minimize risk diversified even when this increased risk. These results indicate that novice investors neglect covariation when diversifying across investment alternatives. Experiment 4 established that naive diversification follows from motivation to minimize risk and showed that covariation neglect was not significantly reduced by informing participants about how covariation affects portfolio risk but was reduced by making participants systematically calculate aggregate returns for diversified portfolios. In order to counteract naive diversification, novice investors need to be better informed about the rationale underlying recommendations to diversify. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A dynamic analysis of interfuel substitution for Swedish heating plants

This paper estimates a dynamic model of interfuel substitution for Swedish heating plants. We use the cost share linear logit model developed by Considine and Mount [Considine, T.J., Mount, T.D., 1984. The use of linear logit models for dynamic input demand systems. Review of Economics and Statistics 66, 434–443]. All estimated own-price elasticities are negative and all cross-price elasticities are positive. The estimated dynamic adjustment rate parameter is small, however, increasing with the size of the plant and time, indicating fast adjustments in the fuel mix when changing relative fuel prices. The estimated model is used to illustrate the effects of two different policy changes.     

Augmenting a Waste Glass Mixture Experiment Study with Additional Glass Components and Experimental Runs

A glass composition variation study (CVS) for high-level waste (HLW) stored in Idaho is being statistically designed and performed in phases over several years. The purpose of the CVS is to investigate and model how HLW-glass properties depend on glass composition. The resulting glass property-composition models will be used to develop desirable glass formulations and for other purposes.

Phases 1 and 2 of the CVS have been completed and are briefly described. This paper focuses on the CVS Phase 3 experimental design, which was chosen to augment the Phase 1 and 2 data with additional data points, as well as to account for additional glass components not studied in Phases 1 and/or 2. In total, 16 glass components were varied in the Phase 3 experimental design. The paper describes how these Phase 3 experimental design augmentation challenges were addressed using the previous data, preliminary property-composition models, and statistical mixture experiment and optimal experimental design methods and software. The resulting Phase 3 experimental design of 30 simulated HLW glasses is presented and discussed.     

TiO2 photocatalysis in cementitious systems: Insights into self-cleaning and depollution chemistry

The present work offers a general overview about application of titanium dioxide (or titania), TiO₂, photocatalysis to concrete technology in relation to enhanced aesthetic durability and depollution properties achieved by implementing TiO₂ into cement. Chemistry of degradation of Rhodamine B (RhB), a red dye used to assess self-cleaning performances of concretes containing TiO₂, as well as oxidation of nitrogen oxides (NOx), gaseous atmospheric pollutants responsible for acid rains and photochemical smog, is investigated using two commercial titania samples in cement and mortar specimens: a microsized, m-TiO₂ (average particle size 153.7 nm ± 48.1 nm) and a nanosized, n-TiO₂ (average particle size 18.4 nm ± 5.0 nm). Experimental data on photocatalytic performances measured for the two samples are discussed in relation to photocatalyst properties and influence of the chemical environment of cement on titania particles. Impacts on applications in construction concrete are also discussed.     

Effects of crossover hydrogen on platinum dissolution and agglomeration

The durability of catalysts in the polymer-electrolyte membrane fuel cell (PEMFC) is identified as a critical limiting factor for wide commercialization of fuel cells. Even though much progress has been made in understanding the degradation mechanisms, the phenomena of Pt dissolution and agglomeration and their contributing factors are not fully understood. In the present investigation, the effects of crossover hydrogen on Pt degradation are studied using an accelerated stress test (AST). The end-of-test (EOT) membrane-electrode-assemblies (MEAs) were characterized by X-ray diffraction (XRD), scanning-electron microscopy (SEM), and energy-dispersive X-ray (EDX). The results provided mechanistic understanding of Pt dissolution and agglomeration: Pt growth and agglomeration were found to be less severe with more crossover hydrogen due likely to the chemical reduction of Pt oxides by crossover hydrogen and the subsequently decrease in the amount of Pt ions formed via the oxide pathway.     

Effect of gas composition on Ru dissolution and crossover in polymer-electrolyte membrane fuel cells

Pt-Ru-based anodes are commonly used in polymer-electrolyte membrane fuel cells (PEMFCs) to provide improved CO tolerance for reformate fuel applications. However, Ru crossover from the anode to the cathode has been identified as a critical durability problem that has severe performance implications. In the present study, an anode accelerated stress test (AST) was used to simulate potential spikes that occur during fuel cell start-ups and shutdowns to induce Ru crossover. The effects of fuel gas composition, namely hydrogen and carbon dioxide concentrations, on Ru dissolution and crossover were investigated. The cell performance losses were correlated with the degree of Ru crossover as determined by the changes in cathode cyclic voltammetry (CV) characteristics and neutron activation analysis (NAA). It was found that higher hydrogen concentration in the fuel accelerated Ru crossover and that the presence of carbon dioxide hindered Ru crossover. In particular, the injection of 20 vol.% carbon dioxide during potential cycling resulted in very minor Ru crossover, which showed essentially identical performance losses and CV characteristic changes as a fuel cell composed of a Ru-free anode. The experimental results suggest that the Ru species in our Pt-Ru metal oxide catalysts need to go through a reduction step by hydrogen before dissolution. The presence of carbon dioxide may play a role in hindering the reduction step.