THE EFFECT OF GEOMETRY ON THE DEVELOPMENT OF CREEP SINGULAR FIELDS FOR DEFECTS UNDER STEP-LOAD CONTROLLED LOADING

Abstract— The development of singular fields for defects in steadily loaded creeping structures is examined as a function of geometry and crack size using finite-element analyses and results from the literature. Approximations for estimating the time-development of the amplitude of the fields are examined and it is shown that simple approximations are expected to apply for a wide range of geometries. It is shown both theoretically and numerically that plasticity on initial loading produces crack tip fields closer to the steady state condition than those produced elastically.     

Structures at elevated temperatures: How long will they last?

In principle, questions about the behaviour of high-temperature structures can be answered by analysis in conjunction with material creep properties. However, because of the wide range of geometries in use, simplified methods have been developed which avoid lengthy computations yet isolate the important factors controlling component behaviour. This paper describes one approach which is to define a reference stress such that the component life is equal to the life of a simple specimen tested at the reference stress. A substantial body of work has shown that the reference stress can often be established quite simply even for complex components containing cracks. The approach then provides a simple framework for assessing structures which operate at high temperatures.     

John Bowlby (1907–1990): Obituary.

Marks the death of John Bowlby, whose Attachment Theory (AT) has had greater impact on American psychology than any theory of personality development since Freud's. Bowlby believed in the importance of real-life experiences in the etiology of mental disorders, rather than in the fantasies that then-current psychoanalytic theory emphasized. He was convinced of the importance to a child's personality development of interaction with its parents. In 1948, he established a research unit at the Tavistock Clinic to continue his work on the effects of early separation and identified 3 phases of response: protest, despair, and detachment. Inspired by the work of Konrad Lorenz, Bowlby seized on ethology and Darwinian evolutionary theory as the foundation of AT. First applied to social development in infancy, AT is now leading to research in later childhood and adulthood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fixed-wavelength operation of a copper-laser-pumped dye laser injection seeded by low-power He-Ne lasers

The design and operating characteristics of a dye laser pumped by a 3-W copper-vapor laser (CVL) and injection seeded by low-power (1-5 mW) He-Ne lasers at 633 nm are reported. An extremely simple optical arrangement is used wherein the output mirror of the He-Ne laser and a third mirror form the dye laser cavity. Laser efficiency in fixed-wavelength operation has been investigated for variable CVL pump power, He-Ne injection power and polarization, and cavity output coupling for a standard Rhodamine 590/Rhodamine 640 dye solution. Over 90% of free-running (unseeded) laser power is obtained in fixed-wavelength (seeded) operation at low CVL pump powers (≤1 W), dropping to approximately 60% at 3-W pump power. Maximum CVL pump to dye laser optical conversion efficiency in narrow-band, fixed-wavelength operation at 633 nm was 12%.     

Emotion understanding and performance during computer-supported collaboration

Individuals collaborating around and through computers benefit from receiving information that helps them understand one another, which is often termed awareness. This article explores what collaborators understand about each other’s emotions and the potential benefits for performance that might come from raising this understanding. In Experiment 1 co-located collaborators judged each other’s emotions after playing a game that required cooperative data collection and analysis. Their judgements were largely inaccurate and based on their own emotions, suggesting limited emotion understanding. Experiment 2 explored if this could be overcome by making collaborators aware of each other’s emotions. Co-located and remote collaborators played a cooperative puzzle-solving game under conditions of awareness or no awareness. Awareness was manipulated by making collaborators share their self-reported emotions during key moments of their game play. Both remote and co-located collaborators improved their performance after sharing their emotions. However, unlike co-located collaborators, remote collaborators also improved their understanding of each other’s emotions and experienced more positive affect. We conclude by discussing the content of collaborators’ emotion understanding and the probable mechanisms underlying the observed effects of being made aware of a partner’s emotions.     

Using mobile media creation to structure museum interpretation with professional vision

Mobile technology plays an increasing role in museum and cultural heritage contexts. In most cases, these tools support the relatively passive consumption of expert interpretations, or the unguided generation of content by users. This paper explores the potential for technologies to help museum visitors, encountering unfamiliar objects, to engage with them as a skilled professional interpreter would, through structured mobile experiences that focus on creating multimedia content. We explore this concept in the area of artefact interpretation and specifically how to enact a structured process of interpretation, as would commonly be taught in courses dedicated to the analytical diagnostics of visual evidence, such as Classical Archaeology or Art History. We discuss two field trials of prototype systems through which the structured creation of multimedia forms a basis for learning to interpret historical artefacts conducted in contexts of both formal and informal learning. By describing, implementing, and evaluating this approach, we contribute understanding of a new way to conceptualise active engagement in museum contexts, through the effective use of scaffolding and user generation of multimedia. We identify issues around the properties and flexibilities of multiple media for this purpose, links between provision for procedural and factual learning, and the value of media creation-based structures in improving the skills and confidence to interpret.     

Photoreduction of Shewanella oneidensis Extracellular Cytochromes by Organic Chromophores and Dye‐Sensitized TiO2

The transfer of photoenergized electrons from extracellular photosensitizers across a bacterial cell envelope to drive intracellular chemical transformations represents an attractive way to harness nature's catalytic machinery for solar‐assisted chemical synthesis. In Shewanella oneidensis MR‐1 (MR‐1), trans‐outer‐membrane electron transfer is performed by the extracellular cytochromes MtrC and OmcA acting together with the outer‐membrane‐spanning porin ? cytochrome complex (MtrAB). Here we demonstrate photoreduction of solutions of MtrC, OmcA, and the MtrCAB complex by soluble photosensitizers: namely, eosin Y, fluorescein, proflavine, flavin, and adenine dinucleotide, as well as by riboflavin and flavin mononucleotide, two compounds secreted by MR‐1. We show photoreduction of MtrC and OmcA adsorbed on Ru^II‐dye‐sensitized TiO₂ nanoparticles and that these protein‐coated particles perform photocatalytic reduction of solutions of MtrC, OmcA, and MtrCAB. These findings provide a framework for informed development of strategies for using the outer‐membrane‐associated cytochromes of MR‐1 for solar‐driven microbial synthesis in natural and engineered bacteria.     

The estimation of J in three-point-bend specimens with a crack in a mismatched weld

The J integral is estimated by using an equivalent stress-strain relationship approach for three-point-bend specimens containing a weld with mismatched mechanical properties. Elastic-plastic finite element analyses are performed to verify the use of this approach. The results show that satisfactory precision can be obtained provided a suitable limit load solution is used. A limit load solution suggested by Burstow is suitable for over-matching situations and a solution due to Joch et al. for under-matching ones.     

h andh-p version error estimation and adaptive procedures from theory to practice

In this paper we introduce techniques that allow us to define a posteriori error estimators via well-known recovery techniques. These allow us to construct a posteriori error estimators for relatively general problems. Further, we introduce new adaptive procedures that make use of these estimators and, in particular, describe anh-p procedure that is simple to implement and that, as numerical experiments have shown, attains an accelerated rate of convergence expected from theh-p version.