Assessment of existing H2/O2 chemical reaction mechanisms at reheat gas turbine conditions

This paper provides detailed comparisons of chemical reaction mechanisms of H₂ applicable at high preheat temperatures and pressures relevant to gas turbine and particularly Alstom’s reheat gas turbine conditions. It is shown that the available reaction mechanisms exhibit large differences in several important elementary reaction coefficients. The reaction mechanisms are assessed by comparing ignition delay and laminar flame speed results obtained from CHEMKIN with available data, however, the amount of data at these conditions is scarce and a recommended candidate among the mechanisms can presently not be selected. Generally, the results with the GRI-Mech and Leeds mechanisms deviate from the Davis, Li, Ó Conaire, Konnov and San Diego mechanisms, but there are also significant deviations between the latter five mechanisms that altogether are better adapted to hydrogen. The differences in ignition delay times between the dedicated hydrogen mechanisms (Ó Conaire, Li and Konnov) range from approximately a maximum factor of 2 for the H₂-air cases, to more than a factor 5 for the H₂/O₂/AR cases. The application of the computed ignition delay time to reheat burner development is briefly discussed.     

Au-Sn SLID Bonding: A Reliable HT Interconnect and Die Attach Technology

Au-Sn solid–liquid interdiffusion (SLID) bonding is an established reliable high temperature (HT) die attach and interconnect technology. This article presents the life cycle of an optimized HT Au-Sn SLID bond, from fabrication, via thermal treatment, to mechanical rupture. The layered structure of a strong and uniform virgin bond was identified by X-ray diffraction to be Au/ζ (Au_0.85Sn_0.15)/Au. During HT exposure, it was transformed to Au/β (Au_1.8Sn_0.2)/Au. After HT exposure, the die shear strength was reduced by 50 pct, from 14 Pa to 70 MPa, which is still remarkably high. Fractographic studies revealed a change in fracture mode; it was changed from a combination of adhesive Au/Ni and cohesive SiC fracture to a cohesive β-phase fracture. Design rules for high quality Au-Sn SLID bonds are given.     

How does project size affect cost estimation error? Statistical artifacts and methodological challenges

Empirical studies differ in what they report as the underlying relation between project size and percent cost overrun. As a consequence, the studies also differ in their project management recommendations. We show that studies with a project size measure based on the actual cost systematically report an increase in percent cost overrun with increased project size, whereas studies with a project size measure based on the estimated cost report a decrease or no change in percent cost overrun with increased project size. The observed pattern is, we argue, to some extent a statistical artifact caused by imperfect correlation between the estimated and the actual cost. We conclude that the previous observational studies cannot be considered to provide reliable evidence in favor of an underlying project size related cost estimation bias. We discuss the limited, statistically robust evidence and the need for other types of studies.     

Geoelectrical imaging in the interpretation of geological conditions affecting quarry operations

Determination of the subsurface geology is very important for the rock quarry industry. This is primarily done by drilling and mapping. However, in Sweden, the bedrock is often completely covered by Quaternary sediments, making the prediction quite difficult. This study shows that electrical resistivity imaging together with induced polarization proved to be very efficient in detecting fracture frequency, major fracture zones and variations in rock mass quality, all of which can affect the aggregate quality. These techniques can also determine the thickness of the overburden. Furthermore, by doing 2D-parallel data sampling, a 3D inversion of the dataset is possible, which greatly enhances the visualization of the subsurface. Implementation of geophysics can be a valuable tool for the quarry industry, resulting in substantial economic benefits.     

A method for the determination of available fluoride from marine products using young chicks

A method is described for the determination of available fluoride in biological materials. Groups of 1-day-old male White Leghorn chicks were fed a low fluoride diet for 14 days (2.3 mg F⁻ kg⁻¹) to which graded levels of fluoride were added as sodium fluoride, or in the form of fluoride-containing foods. The drinking water did not contain any detectable amount of fluoride. Water and feeds were provided ad lib. The response was measured as the concentration of fluoride in the three bones of the third toe from both feet on a fat-free dry matter basis. A linear accumulation was observed for the addition of up to 500 mg F⁻ kg⁻¹ to the diet. An experimental dose range between 0 and 8 mg kg⁻¹ was chosen. The availability of fluoride was measured as the slope ratio between highly correlated regression lines for test material and a standard. The lines had a common intersection on the y-axis. Relative to sodium fluoride, the biological availability of fluoride from different types of fish protein concentrate showed values of 110-151%. The corresponding values for krill (Meganyctiphanes norvegica) and a fluoridated toothpaste containing sodium monofluoro-phosphate were 112 and 145%, respectively.     

Au-Sn SLID Bonding—Properties and Possibilities

Au-Sn solid–liquid interdiffusion (SLID) bonding is a novel and promising interconnect technology for high-temperature applications. This article gives a review over previously published work on Au-Sn SLID bonding. An overview of the crystal phases and the thermomechanical properties of the Au-Sn phases relevant for Au-Sn SLID bonding is given. A summary of the bonding conditions used during Au-Sn SLID bonding is presented together with results from reliability tests. Additional challenges, possibilities, and recommendations for how a reliable high-temperature Au-Sn SLID bonding should be constructed are also discussed.     

A β‐Hairpin‐Binding Protein for Three Different Disease‐Related Amyloidogenic Proteins

Amyloidogenic proteins share a propensity to convert to the β‐structure‐rich amyloid state that is associated with the progression of several protein‐misfolding disorders. Here we show that a single engineered β‐hairpin‐binding protein, the β‐wrapin AS10, binds monomers of three different amyloidogenic proteins, that is, amyloid‐β peptide, α‐synuclein, and islet amyloid polypeptide, with sub‐micromolar affinity. AS10 binding inhibits the aggregation and toxicity of all three proteins. The results demonstrate common conformational preferences and related binding sites in a subset of the amyloidogenic proteins. These commonalities enable the generation of multispecific monomer‐binding agents.     

Fringing fields in a liquid crystal spatial light modulator for beam steering

Abstract

Phase modulating spatial light modulators (SLMs) can be used to alter the shape of a laser wavefront to achieve a deflection or change in the shape of a laser beam. This paper reports the results of characterization, simulation and optimization of a one-dimensional liquid crystal (LC) SLM. The device has a large ratio between LC layer thickness and pixel pitch that results in a fringing field between pixels. In effect, the applied phase patterns will be lowpass filtered and the loss of high frequency components limits, for instance, the usable steering range. A method is presented where intensity measurements in the far field are used to determine how the phase modulation at the SLM is distorted. The inhomogeneous optical anisotropy of the device was determined by modelling the liquid crystal director distribution within the electrode-pixel structure. Finite-difference time-domain (FDTD) simulations were used to calculate the light propagation through the LC. The simulated phase distortion was compared with the experimental results. A voltage compensation scheme to improve the diffraction efficiency was developed utilizing the measured and simulated results. It is demonstrated that a modification of the voltage patterns can give a better realization of high frequency components in the phase distribution and an increase in maximum steering angle by a factor two.     

The effects of request formats on judgment-based effort estimation

In this paper we study the effects of a change from the traditional request “How much effort is required to complete X?” to the alternative “How much can be completed in Y work-hours?”. Studies 1 and 2 report that software professionals receiving the alternative format provided much lower, and presumably more optimistic, effort estimates of the same software development work than those receiving the traditional format. Studies 3 and 4 suggest that the effect belongs to the family of anchoring effects. An implication of our results is that project managers and clients should avoid the alternative estimation request format.     

Experience from Two Resistivity Inversion Techniques Applied in Three Cases of Geotechnical Site Investigation

The combination of in situ geotechnical testing and continuously measured geophysical data can be a powerful tool in geotechnical site investigation. In two cases from Sweden and one case from Denmark electric resistivity surveys are used successfully in geotechnical site investigations. The main contribution of resistivity results is the possibility to interpret continuous geological models. An improved methodology combines two-dimensional (2D) smooth inversion and 2D laterally constrained inversion (2D-LCI) to significantly increase interpretability. The 2D smooth inversion has high horizontal resolution and 2D-LCI high vertical resolution. The possibility to add a priori information from, for example, drill log data to constrain the 2D-LCI increases the confidence in the inverted model and limits ambiguity. In a site investigation for a railway trench in southern Sweden a geotechnical data set is used as a priori data to increase the reliability of the inversion of the resistivity data. From this combined survey a complex Quaternary geology is described in detail. A slope stability study from south of Stockholm, Sweden, employed resistivity data together with refraction seismic and geotechnical drill log data. The result gives necessary geometrical information for the important geological units, for example for stability calculations. Both these surveys were performed with a multielectrode system. In the third case a pulled array resistivity survey was used to map the uppermost 15–20?m to estimate the distribution of the geological formations for freeway construction in Denmark. The result enables a more accurate estimate of the total freeway construction costs.