Some issues in numerical simulation of nonlinear structural response

The development of commercial finite element software is addressed. This software provides practical tools that are used in an astonishingly wide range of engineering applications that include critical aspects of the safety evaluation of nuclear power plants or of heavily loaded offshore structures in the hostile environments of the North Sea or the Arctic, major design activities associated with the development of airframes for high strength and minimum weight, thermal analysis of electronic components, and the design of sports equipment. In the more advanced application areas, the effectiveness of the product depends critically on the quality of the mechanics and mechanics related algorithms that are implemented. Algorithmic robustness is of primary concern. Those methods that should be chosen will maximize reliability with minimal understanding on the part of the user. Computational efficiency is also important because there are always limited resources, and hence problems that are too time consuming or costly. Finally, some areas where research work will provide new methods and improvements is discussed

Water impact analysis of space shuttle solid rocket motor by the finite element method

Preliminary analysis showed that the doubly curved triangular shell elements were too stiff for these shell structures. The doubly curved quadrilateral shell elements were found to give much improved results. A total of six load cases were analyzed in this study. The load cases were either those resulting from a static test using reaction straps to simulate the drop conditions or under assumed hydrodynamic conditions resulting from a drop test. The latter hydrodynamic conditions were obtained through an emperical fit of available data. Results obtained from a linear analysis were found to be consistent with results obtained elsewhere with NASTRAN and BOSOR. The nonlinear analysis showed that the originally assumed loads would result in failure of the shell structures. The nonlinear analysis also showed that it was useful to apply internal pressure as a stabilizing influence on collapse. A final analysis with an updated estimate of load conditions resulted in linear behavior up to full load

The role of elasticity in slab bending

International audiencePrevious studies showed that plate rheology exerts a dominant control on the shape and velocity of subducting plates. Here, we perform a systematic investigation of the role of elasticity in slab bending, using fully dynamic 2-D models where an elastic, viscoelastic, or viscoelastoplastic plate subducts freely into a purely viscous mantle. We derive a scaling relationship between the bending radius of viscoelastic slabs and the Deborah number, De, which is the ratio of Maxwell time over deformation time. We show that De controls the ratio of elastically stored energy over viscously dissipated energy and find that at De>10-2, substantially less energy is required to bend a viscoelastic slab to the same shape as a purely viscous slab with the same intrinsic viscosity. Elastically stored energy at higher De favors retreating modes of subduction via unbending, while trench advance only occurs for some cases with De 1, where most zones have low De 0.1. Slabs with De<10-2 either have very low viscosities or they may be yielding, in which case our De estimates may be underestimated by up to an order of magnitude, potentially pointing towards a significant role of elasticity in ∼60% of the subduction zones. In support of such a role of elasticity in subduction, we find that increasing De correlates with increasing proportion of larger seismic events in both instrumental and historic catalogues

Local festivals, social capital and sustainable destination development: experiences in East London

This paper explores the nature of social capital arising from engagement in local festivals and the implications of this for the social sustainability of an emerging destination. Two case studies are developed from a longitudinal research project which investigates local festivals staged in the Hackney Wick and Fish Island area adjacent to Queen Elizabeth Olympic Park in East London, UK between 2008 and 2014. This area has been directly affected by extensive development and regeneration efforts associated with the staging of the London 2012 Olympic Games. The two festivals considered here respond to the challenges and opportunities arising for local people as the area changes. One festival aims to foster a sense of community by creating shared experiences and improving communication across diverse groups. The other draws together the cultural community, links them to the opportunities arising as the area emerges as a destination, and attracts visitors. These festivals increase social capital in the area, but its distribution is very uneven. The accrual of social capital exacerbates existing inequalities within the host community, favouring the “haves” at the expense of the “have nots”. There are tensions between the development of social capital and social sustainability in this emerging destination

Genetic assessment of ex situ populations to aid species conservation and maintain heterozygosity in non-model species

The number of species classified by the IUCN as endangered or critically endangered is predicted to increase dramatically in the coming decades. During this time, we will also see a parallel rise in the number of captive populations of endangered species. Appropriate genetic management strategies must be implemented to avoid inbreeding depression and heterozygosity loss in these small ex situ populations. Despite strong conservation concern, genetic markers are typically unavailable for threatened species and must be developed, often as a new captive population is being established. These novel markers can then be used to assess the relatedness and diversity of the founding population, inform breeding programmes and make routine assessments after each captive generation; processes which should be standard practice when managing ex situ populations. Here we present a case study in the assessment of genetic health of a captive population of the endangered undulate ray (Raja undulata). Novel microsatellite markers were designed using a next-generation sequencing workflow and primer pairs amplifying eight polymorphic microsatellite loci characterised in 35 captive individuals. Sampling of live individuals used a minimally invasive method and the genotypes determined were used to evaluate the overall genetic diversity of the captive population, predict the relatedness of each pair of individuals and to monitor for changes in the rate of heterozygosity after the first captive generation. Our approach offers a useful roadmap for the rapid assessment of genetic health of ex situ elasmobranch populations, and is also applicable to any captive or wild population requiring genetic management

Reliability of single-lead electrocardiogram interpretation to detect atrial fibrillation: insights from the SAFER feasibility study

Aims: Single-lead electrocardiograms (ECGs) can be recorded using widely available devices such as smartwatches and handheld ECG recorders. Such devices have been approved for atrial fibrillation (AF) detection. However, little evidence exists on the reliability of single-lead ECG interpretation. We aimed to assess the level of agreement on detection of AF by independent cardiologists interpreting single-lead ECGs and to identify factors influencing agreement. Methods and results: In a population-based AF screening study, adults aged ≥65 years old recorded four single-lead ECGs per day for 1–4 weeks using a handheld ECG recorder. Electrocardiograms showing signs of possible AF were identified by a nurse, aided by an automated algorithm. These were reviewed by two independent cardiologists who assigned participant- and ECG-level diagnoses. Inter-rater reliability of AF diagnosis was calculated using linear weighted Cohen’s kappa (κw). Out of 2141 participants and 162 515 ECGs, only 1843 ECGs from 185 participants were reviewed by both cardiologists. Agreement was moderate: κw = 0.48 (95% confidence interval, 0.37–0.58) at participant level and κw = 0.58 (0.53–0.62) at ECG level. At participant level, agreement was associated with the number of adequate-quality ECGs recorded, with higher agreement in participants who recorded at least 67 adequate-quality ECGs. At ECG level, agreement was associated with ECG quality and whether ECGs exhibited algorithm-identified possible AF. Conclusion: Inter-rater reliability of AF diagnosis from single-lead ECGs was found to be moderate in older adults. Strategies to improve reliability might include participant and cardiologist training and designing AF detection programmes to obtain sufficient ECGs for reliable diagnoses

Secondary Stakeholder Influence on CSR Disclosure: An Application of Stakeholder Salience Theory

The aim of this study is to analyse how secondary stakeholders influence managerial decision-making on Corporate Social Responsibility (CSR) disclosure. Based on stakeholder salience theory, we empirically investigate whether differences in environmental disclosure among companies are systematically related to differences in the level of power, urgency and legitimacy of the environmental non-governmental organisations (NGOs) with which these companies are confronted. Using proprietary archival data for an international sample of 199 large companies, our results suggest that differences in environmental disclosures between companies are mainly associated with differences between their environmental stakeholders’ legitimacy. The effects of power and urgency are of an indirect nature, as they are mediated by legitimacy. This study improves our understanding of CSR disclosure by demonstrating that, next to the well-documented effect of company characteristics, stakeholder characteristics are also important. Besides, it provides scarce empirical evidence that not only primary stakeholders, but also secondary stakeholders are influential with regards to management decision-making. And more specifically, it offers insight into why some stakeholder groups are better able to influence disclosure decisions than other. The results also have important practical implications for managers of both environmental NGOs and large companies. For managers of environmental NGOs the results provide evidence of the most successful tactics for having their environmental information demands satisfied by companies. For company management the results provide insights into the most important stakeholder characteristics, on the basis of which they may develop strategies for proactively disclosing environmental information

Keratin and S100 calcium-binding proteins are major constituents of the bovine teat canal lining

The bovine teat canal provides the first-line of defence against pathogenic bacteria infecting the mammary gland, yet the protein composition and host-defence functionality of the teat canal lining (TCL) are not well characterised. In this study, TCL collected from six healthy lactating dairy cows was subjected to two-dimensional electrophoresis (2-DE) and mass spectrometry. The abundance and location of selected identified proteins were determined by western blotting and fluorescence immunohistochemistry. The variability of abundance among individual cows was also investigated. Two dominant clusters of proteins were detected in the TCL, comprising members of the keratin and S100 families of proteins. The S100 proteins were localised to the teat canal keratinocytes and were particularly predominant in the cornified outermost layer of the teat canal epithelium. Significant between-animal variation in the abundance of the S100 proteins in the TCL was demonstrated. Four of the six identified S100 proteins have been reported to have antimicrobial activity, suggesting that the TCL has additional functionality beyond being a physical barrier to invading microorganisms. These findings provide new insights into understanding host-defence of the teat canal and resistance of cows to mastitis

Practical Aspects of Finite Element Computations in Solid Mechanics

The paper focuses on practical aspects of the prospective use of finite element methods in problems in solid mechanics. It looks briefly at the computer and computer language environment in which the methods are used, and at the computational aspects of the numerical method itself. The fundamental algorithmic problems (spatial and temporal discretization, and the modeling of realistic material behaviors) are reviewed from an applications viewpoint, and some areas where further work is needed are mentioned.</jats:p