Thermal boundary effects on a GT liner structure

GT combustor liners are subjected to mechanical and thermal loads that damage the structure and reduce their operational life. Among those, the thermo-acoustic instabilities develop, generating pressure oscillations because of the interaction between heat release, acoustic waves and structure vibrations. The vibratory behaviour of the structure is the result of these phenomena and undergoes repeated reversals of the main deformation mechanisms as a function of the operating load of the engine. Monitoring and evaluating the operational load history and the life consumption rate of combustor components is essential to sustain a reliable risk-based maintenance in the GT combustion hardware. The non-linear material behaviour can activate possible interactions causing coupled damage mechanisms and become a life threatening mode of failure. A methodology for modelling both the dynamic and static behaviour of a GT cannular combustion chamber by utilizing a combined fluid-structure approach is presented in this study. Together with the calculation of the heat fluxes through the liner, the effects of the modifications at the thermal boundary conditions were used to investigate the modifications in the liner structural properties and the stresses development at different GT loads. The monitored pressure oscillations during operations has been investigated by performing both acoustic and structural dynamics. A correlation with the observed failure has been proposed by investigating stress relaxation phenomena’s, creep and plastic effects for base load and part load operations

Can dissonance engineering improve risk analysis of human–machine systems?

The paper discusses dissonance engineering and its application to risk analysis of human–machine systems. Dissonance engineering relates to sciences and technologies relevant to dissonances, defined as conflicts between knowledge. The richness of the concept of dissonance is illustrated by a taxonomy that covers a variety of cognitive and organisational dissonances based on different conflict modes and baselines of their analysis. Knowledge control is discussed and related to strategies for accepting or rejecting dissonances. This acceptability process can be justified by a risk analysis of dissonances which takes into account their positive and negative impacts and several assessment criteria. A risk analysis method is presented and discussed along with practical examples of application. The paper then provides key points to motivate the development of risk analysis methods dedicated to dissonances in order to identify the balance between the positive and negative impacts and to improve the design and use of future human–machine system by reinforcing knowledge

Electromagnetic radiative corrections in parity-violating electron-proton scattering

QED radiative corrections have been calculated for leptonic and hadronic variables in parity-violating elastic ep scattering. For the first time, the calculation of the asymmetry in the elastic radiative tail is performed without the peaking-approximation assumption in hadronic variables configuration. A comparison with the PV-A4 data validates our approach. This method has been also used to evaluate the radiative corrections to the parity-violating asymmetry measured in the G0 experiment. The results obtained are here presented.Comment: 12 pages, 11 figure

Structure analysis of the virtual Compton scattering amplitude at low energies

We analyze virtual Compton scattering off the nucleon at low energies in a covariant, model-independent formalism. We define a set of invariant functions which, once the irregular nucleon pole terms have been subtracted in a gauge-invariant fashion, is free of poles and kinematical zeros. The covariant treatment naturally allows one to implement the constraints due to Lorentz and gauge invariance, crossing symmetry, and the discrete symmetries. In particular, when applied to the $ep\to e'p'\gamma$ reaction, charge-conjugation symmetry in combination with nucleon crossing generates four relations among the ten originally proposed generalized polarizabilities of the nucleon.Comment: 19 pages, LaTeX2e/RevTeX, no figures, original sections IV.-VI. removed, to be discussed in a separate publication, none of the conclusions change

Virtual Compton Scattering off the Nucleon in Chiral Perturbation Theory

We investigate the spin-independent part of the virtual Compton scattering (VCS) amplitude off the nucleon within the framework of chiral perturbation theory. We perform a consistent calculation to third order in external momenta according to Weinberg's power counting. With this calculation we can determine the second- and fourth-order structure-dependent coefficients of the general low-energy expansion of the spin-averaged VCS amplitude based on gauge invariance, crossing symmetry and the discrete symmetries. We discuss the kinematical regime to which our calculation can be applied and compare our expansion with the multipole expansion by Guichon, Liu and Thomas. We establish the connection of our calculation with the generalized polarizabilities of the nucleon where it is possible.Comment: 26 pages, 2 Postscript figures, RevTex using epsfi

Ethical challenges in nephrology : a call for action

The American Society of Nephrology, the European Renal Association-European Dialysis and Transplant Association and the International Society of Nephrology Joint Working Group on Ethical Issues in Nephrology have identified ten broad areas of ethical concern as priority challenges that require collaborative action. Here, we describe these challenges - equity in access to kidney failure care, avoiding futile dialysis, reducing dialysis costs, shared decision-making in kidney failure care, living donor risk evaluation and decision-making, priority setting in kidney disease prevention and care, the ethical implications of genetic kidney diseases, responsible advocacy for kidney health and management of conflicts of interest - with the aim of highlighting the need for ethical analysis of specific issues, as well as for the development of tools and training to support clinicians who treat patients with kidney disease in practising ethically and contributing to ethical policy-making. Here, the ASN-ERA-EDTA-ISN Joint Working Group on Ethical Issues in Nephrology highlights ten areas of ethical concern as priority challenges that require collaborative action and discusses the need for development of ethical training and guidance tools to manage these issues

Identification of a Protein with Antioxidant Activity that is Important for the Protection against Beer Ageing

This study was carried out with fresh Australian lager beer which was sampled directly off the production line, the same samples aged for 12 weeks at 30 °C, and the vintage beer which was kept at 20 °C for 5 years. Characteristic Australian lager flavour was maintained in the fresh and vintage beers but was lost in the aged beer. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and free thiol group labelling analyses of beer proteins found that this flavour stability correlated with the presence of an unknown 10 kilodaltons (kDa) protein with a higher level of free thiols. The protein was purified by size-exclusion chromatography, then peptide sequencing and database matching identified it as the barley lipid transfer protein (LTP1). Further characterisation using diphenylpicrylhydrazyl (DPPH) free radical scavenging and a Saccharomyces cerevisiae-based antioxidant screening assay demonstrated that the LTP1 protein was active in DPPH reduction and antioxidant activity. The absence of free thiol in the aged beer indicates that the thiol functional groups within the LTP1 protein were saturated and suggests that it is important in the flavour stability of beer by maintaining reduction capacity during the ageing process

Assessing contextual descriptive features for plot-based classification of urban areas

A methodology for mapping urban land-use types integrating information from multiple data sources (high spatial resolution imagery, LiDAR data, and cadastral plots) is presented. A large set of complementary descriptive features that allow distinguishing different urban structures (historical, urban, residential, and industrial) is extracted and, after a selection process, a plot-based image classification approach applied, facilitating to directly relate the classification results and the urban descriptive parameters computed to the existent land-use/land-cover units in geospatial databases. The descriptive features are extracted by considering different hierarchical scale levels with semantic meaning in urban environments: buildings, plots, and urban blocks. Plots are characterised by means of image-based (spectral and textural), three-dimensional, and geometrical features. In addition, two groups of contextual features are defined: internal and external. Internal contextual features describe the main land cover types inside the plot (buildings and vegetation). External contextual features describe each object in terms of the properties of the urban block to which it belongs. After the evaluation in an heterogeneous Mediterranean urban area, the land-use classification accuracy values obtained show that the complementary descriptive features proposed improve the characterisation of urban typologies. A progressive introduction of the different groups of descriptive features in the classification tests show how the subsequent addition of internal and external contextual features have a positive effect by increasing the final accuracy of the urban classes considered in this study. © 2012 Elsevier B.V.The authors appreciate the financial support provided by the Spanish Ministry of Science and Innovation and FEDER in the framework of the projects CGL2009-14220 and CGL2010-19591/BTE, and the support of the Spanish Instituto Geografico Nacional (IGN).Hermosilla, T.; Ruiz Fernández, LÁ.; Recio Recio, JA.; Cambra López, M. (2012). Assessing contextual descriptive features for plot-based classification of urban areas. Landscape and Urban Planning. 106(1):124-137. doi:10.1016/j.landurbplan.2012.02.008S124137106

Pursuing climate resilient coffee in Ethiopia – a critical review

This paper provides a multi-scalar examination of the Ethiopian coffee sector and its pursuit of climate resilience. Concern is growing about the potential impact of climate change on Arabica coffee in Ethiopia and the 25 million livelihoods it supports. Arabica coffee has a relatively narrow envelope of climatic suitability and recent studies suggest that the area of bioclimatically suitable space for the species in its native Ethiopia could decline dra- matically in the coming decades. We adopt a critical perspective on resilience that reflects on the situated nature of the ecology/science of coffee and climate change and the operation of social, economic, and discursive power across scales, paying particular attention to the differentiated impacts of climate change and associated resi- lience strategies. This analysis begins by reviewing Ethiopia’s Climate Resilient Green Economy strategy and argues that the current lack of attention to coffee is inappropriate considering the coffee sector’s vulnerability to climate change, economic importance and association with forests. The paper then examines the contemporary coffee sector which provides the context for reflecting on three potential responses to the threat climate change poses; a spatial response from farmers, adaptive farm management responses such as changing shade levels and the development of the country’s genetic resources to cultivate improved varieties. The analysis explores the disconnect between the interventions emerging from national and international institutions and the local con- text. The multi-scale approach highlights the presence of complex normative trade-offs associated with pursing climate resilience strategies and reinforces the importance of appreciating the dynamics which influence deci- sion-making in the country