Oxygen Tracer Diffusion in Vitreous Silica

Oxygen diffusion in vitreous silica glass is studied using the gas exchange technique. The tracer concentration profiles are consistent with a model based on two mechanisms, one network and the other interstitial. These processes are coupled through limited network–interstitial exchange. Nuclear reaction analysis and secondary ion mass spectrometry techniques are performed and compared. These results are compared to experiments on transport in thin silica films grown on single-crystal silicon.     

“Leagile” software development: An experience report analysis of the application of lean approaches in agile software development

In recent years there has been a noticeable shift in attention from those who use agile software development toward lean software development, often labelled as a shift “from agile to lean”. However, the reality may not be as simple or linear as this label implies. To provide a better understanding of lean software development approaches and how they are applied in agile software development, we have examined 30 experience reports published in past agile software conferences in which experiences of applying lean approaches in agile software development were reported. The analysis identified six types of lean application. The results of our study show that lean can be applied in agile processes in different manners for different purposes. Lean concepts, principles and practices are most often used for continuous agile process improvement, with the most recent introduction being the kanban approach, introducing a continuous, flow-based substitute to time-boxed agile processes.     

Experimental and numerical evaluation of electromagnetic acoustic transducer performance on steel materials

Electromagnetic Acoustic Transducers (EMATs) are an attractive alternative to standard piezoelectric probes in a number of applications thanks to their contactless nature. EMATs do not require any couplant liquid and are able to generate a wide range of wave-modes; however these positive features are partly counterbalanced by a relatively low signal-to-noise ratio and by the dependence of EMAT performance on the material properties of the test object. A wide variety of steel materials is employed in many industrial applications, so it is important to assess the material-dependent behaviour of EMATs when used in the inspection of different types of steel. Experimental data showing the performance of bulk shear wave EMATs on a wide range of steels is presented, showing the typical range of physical properties encountered in practice. A previously validated Finite Element model, including the main transduction mechanisms, the Lorentz force and magnetostriction, is used to evaluate the experimental data. The main conclusion is that the Lorentz force is the dominant transduction effect, regardless of the magnitude and direction of the bias magnetic field. Differently from magnetostriction, the Lorentz force is not significantly sensitive to the typical range of physical properties of steels, as a consequence the same EMAT sensor can be used on different grades of ferritic steel.     

Artificial disbonds for calibration of transient thermography inspection of thermal barrier coating systems

Transient thermography is commonly used for the detection of disbonds in thermal barrier coatings (TBC). As for other NDT techniques, reference test specimens are required for calibration, but unfortunately, real disbonds are very difficult to use because it is difficult to control their size, and large ones tend to spall. Flat bottomed holes are commonly used, but these over-estimate the thermal contrast obtained for a defect of a given diameter. This paper quantifies the differences in thermal response using finite element analysis validated by experiments, and proposes a form of artificial disbond that gives a better representation of the thermal responses seen with real defects. Real disbonds tend to have a non-uniform gap between the disbonded surfaces across the defect, and the effect of this on the thermal response is evaluated using finite element simulations. It is shown that the effect can be compensated for by adjusting the diameter of the calibration defect compared to the real defect.     

On a fast, compact approximation of the exponential function

Recently Schraudolph (1999) described an ingenious, fast, and compact approximation of the exponential function through manipulation of the components of a standard (IEEE-754 (IEEE, 1985)) floating-point representation. This brief note communicates a recoding of this procedure that overcomes some of the limitations of the original macro at little or no additional computational expense.     

Peer reviewed: environmental sleuth at work

A combination of technical approaches and forensic tools can determine historic causes, timing, and impacts of site contamination.     

Integrin receptors and hairy cell leukaemia

The ability of a cell to recognize and specifically localise within an appropriate tissue environment is essential to the proliferation and survival of that cell. The integrin family of cell-surface adhesion-receptors are essential to such tissue localisation, allowing a migrating cell to specifically recognise, localise within-, and respond to- the cellular or extracellular matrix ligands that characterise a given tissue. We have investigated how the expression and activity of integrin receptors underlies the consistent and unusual tissue distribution of the malignant B lymphocytes of hairy cell leukaemia (HCL). In this report we review our published work in this area. Our findings are then discussed within the context of current knowledge of integrin receptors and their ligands, and in relation to the clinical features of HCL.     

Broadband and digital ‘content’ in the EU-25: Recent trends and challenges

This paper focuses on recent trends and issues in the EU-25 countries related to one key broadband application area: digital media ‘content’ applications. It draws upon recently completed research addressing current and future uses and applications of broadband in the EU-25 area.

The paper presents key findings from the BEACON project concerning the broadband content trends and issues in the EU-25 countries. First, the paper briefly considers recent literature on broadband and digital media innovations as well as the policy context in Europe, which has an important influence on framing supports for innovation in content and digital media. Next, it addresses a number of key issues that impact upon the creation of content services. These include the high cost of content production and the difficulty of forming attractive business cases given the uncertainties related to user demand, and the IPR and copyright regimes. It will also consider users’ patterns of engagement with broadband content and emerging user applications. Next, the paper discusses whether broadband is reaching a ‘tipping point’, whereby broadband access is becoming the norm and in the next five years we will see the emergence of innovative, dynamic content services. The paper considers whether recent moves by three sets of significant actors (media corporations, the advertising sector, and EC regulators) could be early signs of a tipping point in favour of the creation of and more focused support for broadband content services.     

Stress Concentration Due to Fiber-Matrix Fusion in Ceramic-Matrix Composites

Stress concentration in ceramic-matrix composites due to fiber-matrix fusion is investigated using finite-element modeling (FEM) in conjunction with experiment. FEM results indicate substantial stress concentration can be expected when the fiber and matrix are locally fused. The focus of the investigation is sealing through the formation of a reaction product layer (e.g., SiO₂ in a SiC-SiC system). Direct sealing also is considered. Tensile experiments involving a novel SiC-SiC microcomposite system confirm FEM predictions and unambiguously indicate the observed reduction in load-bearing capacity is the result of a SiO₂ reaction product that locally fuses the fiber and matrix.     

An approximate model for three-dimensional alternating current potential drop analyses using a commercial finite element code

Alternating current potential drop (ACPD) is an established technique for non-destructive testing and materials characterisation. Finite element (FE) simulation is a very useful tool for the optimisation of probes and the prediction of test results, but three-dimensional models of ACPD problems are computationally intensive. This paper presents a new, simple model in which frequency-related effects are taken into account by appropriately modifying the geometry of the modelled structure: a DC analysis can then be performed on a smaller domain, thus reducing the computational power required. The results of experimental tests for the validation of the model are also presented and discussed.