Pure rotational coherent anti-Stokes Raman spectroscopy in mixtures of CO and N2

We present a model for quantitative measurements in binary mixtures of nitrogen and carbon monoxide by the use of dual-broadband rotational coherent anti-Stokes Raman spectroscopy. The model has been compared with experimental rotational coherent anti-Stokes Raman scattering spectra recorded within the temperature range of 294-702 K. Temperatures and concentrations were evaluated by spectral fits using libraries of theoretically calculated spectra. The relative error of the temperature measurements was 1-2%, and the absolute error of the CO concentration measurements was <0.5% for temperatures < or =600 K. For higher temperatures, the gas composition was not chemically stable, and we observed a conversion of CO to CO2. The influence of important spectroscopic parameters such as the anisotropic polarizability and Raman line-broadening coefficients are discussed in terms of concentration measurements. In particular, it is shown that the CO concentration measurement was more accurate if N2-CO and CO-N2 line-broadening coefficients were included in the calculation. The applicability of the model for quantitative flame measurements is demonstrated by measuring CO concentrations in ethylene/air flames.     

SAW COM-parameter extraction in AlN/diamond layered structures

Highly c-axis oriented aluminum nitride (AlN) thin piezoelectric films have been grown on polycrystalline diamond substrates by pulsed direct current (DC) magnetron reactive sputter-deposition. The films were deposited at a substrate temperature below 50/spl deg/C (room temperature) and had a typical full width half maximum (FWHM) value of the rocking curve of the AlN-002-peak of 2.1 degrees. A variety of one-port surface acoustic wave (SAW) resonators have been designed and fabricated on top of the AlN films. The measurements indicate that various SAW modes are excited. The SAW phase velocities of up to 11.800 m/s have been measured. These results are in agreement with calculated dispersion curves of the AlN/diamond structure. Finally, the coupling of modes parameters have been extracted from S/sub 11/ measurements using curve fitting for the first SAW mode, which indicate an effective coupling K/sup 2/ of 0.91% and a Q factor of about 600 at a frequency of 1050 MHz.     

Globally Optimal Estimates for Geometric Reconstruction Problems

We introduce a framework for computing statistically optimal estimates of geometric reconstruction problems. While traditional algorithms often suffer from either local minima or non-optimality—or a combination of both—we pursue the goal of achieving global solutions of the statistically optimal cost-function. Our approach is based on a hierarchy of convex relaxations to solve non-convex optimization problems with polynomials. These convex relaxations generate a monotone sequence of lower bounds and we show how one can detect whether the global optimum is attained at a given relaxation. The technique is applied to a number of classical vision problems: triangulation, camera pose, homography estimation and last, but not least, epipolar geometry estimation. Experimental validation on both synthetic and real data is provided. In practice, only a few relaxations are needed for attaining the global optimum.     

Cost-effective energy carriers for transport – The role of the energy supply system in a carbon-constrained world

The aim of this study is to examine how the options for producing electricity, fuels, and heat in a carbon-constrained world affect the cost-effectiveness of a range of fuels and propulsion technologies in the transportation sector. GET 7.0, a global energy system model with five end-use sectors, is used for the analysis. We find that an energy system dominated either by solar or by nuclear tends to make biofuels in plug-in hybrids cost-effective. If coal with carbon capture and storage (CCS) dominates the energy system, hydrogen cars, rather than plug-in hybrids tend to become cost-effective. Performing a Monte Carlo simulation, we then show that the general features of our results hold for a wide range of assumptions for the costs of vehicle propulsion technologies (e.g., batteries and fuel cells). However, sufficiently large changes in say the battery costs may overturn the impact of changes in the energy supply system, so that plug-in hybrid vehicles become cost-effective even if coal with CCS dominate the energy supply. We conclude that analyses of future energy carriers and propulsion technologies need to consider developments in the energy supply system.     

Emission control of nitrogen oxides in the oxy-fuel process

The interest in oxy-combustion as a method to capture carbon dioxide has increased drastically during recent years. The oxy-fuel process offers new process conditions and may take advantage of innovative techniques as well as of new ways to apply conventional measures for emission control. The present work reviews available techniques for controlling both the emission of nitrogen oxides (NO_x) to the atmosphere and the content of NO_x in the captured carbon dioxide. The results indicate that for a first generation of oxy-fuel power plants, conventional primary NO_x control should be sufficient to meet today's emission regulations, if based on emission per unit of fuel supplied. However, there are several opportunities for new methods of NO_x control in oxy-fuel plants, depending on future emission and storage legislation for carbon capture schemes. Improved understanding of the behaviour of nitric oxide and nitrogen dioxide during compression and condensation of carbon dioxide is needed, as well as improved knowledge on the influence of the parameters of oxy-combustion on nitrogen chemistry.     

Exposure of cadmium from infant formulas and weaning foods

Cadmium levels were determined in 59 baby food samples, including milk-based, cereal and milk-based and soy-based formulas, recommended from 0 to 18 months of age. Determinations were performed by Zeeman graphite furnace atomic absorption spectrophotometry, after dry ashing, with parallel determinations of certified reference samples. Mean cadmium levels were found to range from 1.10 to 23.5 mu g / kg fresh weight concentrated formulas. L evels were related to the composition of the diets. Formulas based on cow's milk had the lowest concentrations. Soy formulas contained approximately six times more cadmium than cow's milk formulas, and diets with a cereal content had 4-21 times higher mean levels. The mean weekly intakes of dietary cadmium were estimated to vary between 0.10 and 3 : 05 mu g / kg body weight of the child, if the recommended amount of formula were to be consumed at the recommended age, and if the child were of average weight. This estimation however does not include the contribution of cadmium from drinking water. The highest intake on a body weight basis was found in 6-month-old children, consuming the recommended amount of wheat-, oat- and milk-based formulas. This intake is below the provisional tolerable weekly intake (PTW I) of 7 mu g / kg body weight, established by a W HO/FAO expert group. However, the risk assessment is based on renal effects in adults. Furthermore, preparations of a formula by adding water with cadmium concentrations at the W HO guideline level could lead to intakes at the PTW I level. Compared to breast-fed children, the exposure of dietary cadmium from weaning diets can be up to 12 times higher in children fed infant formula.     

Durability of concrete — Degradation phenomena involving detrimental chemical reactions

While interacting with its service environment, concrete often undergoes significant alterations that often have significant adverse consequences on its engineering properties. As a result, the durability of hydrated cement systems and their constituent phases has received significant attention from scientists and engineers. Cement paste deterioration by detrimental chemical reactions is discussed. First, the mechanisms that govern the transport of ions, moisture and gas are described. Then, different chemical degradation phenomena are reviewed. Microstructural alterations resulting from exposure to chlorides and carbon dioxide are discussed. Sulfate attack from external sources is described including processes resulting in the formation of ettringite and thaumasite. The mineralogy of Portland cement is sensitive to temperature and thermal cycling, particularly during the early hydration period.     

Scratch testing of metals and polymers: Experiments and numerics

An experimental and numerical study of the scratch test performed on metals and polymers was conducted. The materials tested, being both metallic and polymeric, were related to the well known Johnson’s parameter, often used to correlate indentation experiments. The aim was to determine whether it was possible to use the numerical approach presented by Wredenberg and Larsson [F. Wredenberg, P.-L. Larsson, On the numerics and correlation of scratch testing, Journal of Mechanics of Materials and Structures 2 (2006) 573–594] to describe the scratch mechanism and of course also to investigate whether or not important scratch quantities can be determined with sufficient accuracy from standard scratch experiments.