Characterization of Iron Oxides Commonly Formed as Corrosion Products on Steel

For fundamental studies of the atmospheric corrosion of steel, it is useful to identify the iron oxide phases present in rust layers. The nine iron oxide phases, iron hydroxide (Fe(OH)₂), iron trihydroxide (Fe(OH)₃), goethite (α-FeOOH), akaganeite (β-FeOOH), lepidocrocite (γ-FeOOH), feroxyhite (δ-FeOOH), hematite (α-Fe₂O₃), maghemite (γ-Fe₂O₃) and magnetite (Fe₃O₄) are among those which have been reported to be present in the corrosion coatings on steel. Each iron oxide phase is uniquely characterized by different hyperfine parameters from M?ssbauer analysis, at temperatures of 300K, 77K and 4K. Many of these oxide phases can also be identified by use of Raman spectroscopy. The relative fraction of each iron oxide can be accurately determined from the M?ssbauer subspectral area and recoil-free fraction of each phase. The different M?ssbauer geometries also provide some depth dependent phase identification for corrosion layers present on the steel substrate. Micro-Raman spectroscopy can be used to uniquely identify each iron oxide phase to a high spatial resolution of about 1 μm. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mössbauer Studies of Stannous Fluoride Reactivity with Synthetic Tooth Enamel – A Model for the Tooth Cavity Protection Actions of Novel Dentifrices

Hyperfine Interactions - SnF2 is an important toothpaste ingredient, added for the provision of clinical efficacy for hard and soft tissue diseases and in breath protection. Synthetic calcium...     

Eigen analysis of the stability and degree of information content in correlation matrices constructed from property time series data

Property is an asset which forms part of the portfolios of many investors, particularly institutional ones, along with equities and bonds. Techniques from physics, particularly that of random matrix theory, have provided powerful insights into the behaviour of financial assets. A large database providing time series data for over 10,000 individual properties is available for the UK. Some of the data is available at an annual and some at a monthly frequency. However, even at the monthly frequency, only a relatively small number of observations is available, certainly in comparison with that available with financial assets. A key issue in translating methods of analysis in financial markets to property data is whether they are applicable given the small number of data points available. This paper addresses this issue. Using the tools of random matrix theory, we find that a great deal of information is contained within property data. The correlations between different types and geographical locations of property tend to have far more true information and be more stable over time than is the case with financial data, despite the large number of observations available with the latter. Received 31 December 2001     

A Simple Proof of a Theorem of Whyte

Kevin Whyte showed that all Baumslag–Solitar groups BS(p,q) with 1 < p < q are quasi-isometric [Whyte, K., Geom. Funct. Anal. 11 (2001), 1327–1343]. We provide an elementary geometric proof.     

Within-group common weights in DEA: An analysis of power plant efficiency

In many real world applications where DEA is applied, DMUs can often be put into groups, such as those which may be under a single management team. This often means that the multipliers used within a group should be common across that group’s members. The case example examined in this regard is one involving a set of power plants, with each containing a set of power units under a common plant management. We develop a goal-programming model for this setting that seeks to derive such a common-multiplier set. The important feature of this multiplier set is that it minimizes the maximum discrepancy among the within-group scores from their ideal levels.     

Moment-method analysis of printed wire spirals using curvedpiecewise sinusoidal subdomain basis and testing functions

Archimedian and logarithmic printed wire spirals are analyzed using a moment-method incorporating curved piecewise sinusoidal subdomain basis and testing functions. Results for spiral parameters including input impedance and current distribution are presented and are shown to have good agreement with published results for the same antennas obtained using linear segmentation. Since the curved basis functions exactly follow the spiral contour, significantly fewer curved segments are, therefore, required for accurate analysis compared with linear segmentation     

Performance analysis and optimal parameter selection for PYRAMID

Previously, we have proposed PYRAMID, a hierarchical, rule-based scheme for proximity effect correction in electron-beam lithography. In this paper we present a performance analysis of PYRAMID for a variety of different system parameters (resist thickness, substrate composition, etc.). We also discuss the optimal choice of two key correction parameters: global exposure block size and local exposure window size.     

Isothermal aging of near-eutectic Sn-Ag-Cu solder alloys and its effect on electrical resistivity

Solder joints were prepared from seven eutectic and near-eutectic Sn-based compositions and characterized for electrical resistivity after 100 h and 1,000 h of isothermal aging at 423 K. The solder joint samples were prepared by hand soldering to copper substrates, and the post-heat treatment resistivity was measured at room temperature in a specially designed, four-point probe fixture. Compositions tested included Sn-3.5Ag, Sn-3.7Ag-0.9Cu, Sn-3.0Ag-0.5Cu, Sn-3.6Ag-1.0Cu, and Sn-3.9Ag-0.6Cu. In addition, the effect of a minor addition of a fourth element, designed to improve high-temperature shear strength, was also evaluated in the compositions Sn-3.7Ag-0.6Cu-0.3Co and Sn-3.7Ag-0.7Cu-0.2Fe. The observed changes in electrical resistivity are discussed in terms of microstructural coarsening, diffusional transport from the substrate, and nucleation of precipitate phases.