Effects of process parameters upon the shape memory and pseudo-elastic behaviors of laser-welded NiTi thin foil

This article discusses the effects of laser welding parameters such as power, welding speed, and focus position on the weld bead profile, microstructure, pseudo-elasticity (PE), and shape memory effect (SME) of NiTi foil with thickness of 250 um using 100W CW fiber laser. The parameter settings to produce the NiTi welds for analysis in this article were chosen from a fractional factorial design to ensure the welds produced were free of any apparent defect. The welds obtained were mainly of cellular dendrites with grain sizes ranging from 2.5 to 4.8 um at the weld centerline. A small amount of Ni3Ti was found in the welds. The onset of transformation temperatures (As and Ms) of the NiTi welds shifted to the negative side as compared to the as-received NiTi alloy. Ultimate tensile stress of the NiTi welds was comparable to the as received NiTi alloy, but a little reduction in the pseudo-elastic property was noted. Full penetration welds with desirable weld bead profiles and mechanical properties were successfully obtained in this study.

Laser welding of thin foil nickel–titanium shape memory alloy

In this study, two L27 Taguchi experiments were carried out to study the effect of fibre laser welding parameters and their interactions upon the weld bead aspect ratio of nickel–titanium thin foil. The optimum parameters to produce full penetrated weld with the largest aspect ratio and desirable microstructure were successfully obtained by the Taguchi experimental design. The corrosion property of the optimized NiTi weld in Hank’s solution at 37.5 °C was studied and compared with the as-received NiTi. To improve the corrosion properties of the weld, the effect of post-weld-heat-treatments ranging from 573 to 1173 K was investigated. The corrosion properties, surface morphology, microstructure and Ti/Ni ratio of the heat-treated NiTi weld were analysed. It was found that a post-weld heat treatment at 573 K for 1 h provided the best pitting corrosion resistance at the weld zone.

Conference proceedings: Gardening Time: Reflections on Memory, Monuments and History in Sardinia and Scotland.

S. Stoddart and Malone, C. (eds) In Prep. 2013-4 Oxford, Oxbow Books. 25+ themed papers

Relaunching Titanic: Memory and Marketing in the New Belfast

Relaunching Titanic critically considers the invocation of Titanic heritage in Belfast in contributing to a new ‘post-conflict’ understanding of the city. The authors address how the memory of Titanic is being and should be represented in the place of its origin, from where it was launched into the collective consciousness and unconscious of western civilization.

Relaunching Titanic examines the issues in the context of international debates on the tension between place marketing of cities and other alternative portrayals of memory and meaning in places. Key questions include the extent to which the goals of economic development are congruous with the ‘contemplative city’ and especially the need for mature and creative reflection in the ‘post-conflict’ city, whether development interests have taken precedence over the need for a deeper appreciation of a more nuanced Titanic legacy in the city of Belfast, and what Belfast shares with other places in considering the sacred and profane in memory construction.

While Relaunching Titanic focuses on the conflicted history of Belfast and the Titanic, it will have lessons for planners and scholars of city branding, tourism, and urban re-imaging.

Violence and social memory in twentieth century Belfast:Stories of Buck Alec Robinson

This article explores the life and commemoration of Buck Alec Robinson. A feared loyalist killer in 1920s Belfast, in more recent times he has featured as a lion-keeping “character” on wall murals and in tourist guide books. Robinson is employed as a case study to investigate two separate but, in this case, interlinked historiographical debates. The first involves Norbert Elias’s analysis of the decline of violence. The second relates to discussion of the analysis of social memory in working class communities, with violence being placed therein. The article supports historical assessments suggesting that the “civilizing offensive” had an uneven impact. That point is usually made in the context of working class men. This article extends it to political elites in Belfast and probes their flirtations with violent hard men. The case is made that it is a mistake to assume the “civilizing” dynamic is to be understood as a teleological or top-down process.

Reduction of environmentally induced cracking of laser-welded shape memory NiTi wires via post-weld heat-treatment

In this study, the environmentally induced cracking behaviour of the NiTi weldment with and without post-weld heat-treatment (PWHT) in Hanks’ solution at 37.5 °C at OCP were studied by tensile and cyclic slow-strain-rate tests (SSRT), and compared with those tested in oil (an inert environment). Our previous results in the tensile and cyclic SSRT showed that the weldment without PWHT showed high susceptibility to the hydrogen cracking, as evidenced by the degradation of tensile and super-elastic properties when testing in Hanks' solution. The weldment after PWHT was much less susceptible to hydrogen attack in Hanks' solution as no obvious degradation in the tensile and super-elastic properties was observed, and only a very small amount of micro-cracks were found in the fracture surface. The susceptibility to hydrogen cracking of the NiTi weldment could be alleviated by applying PWHT at the optimized temperature of 350 °C after laser welding.

The role of semantic interference in limiting memory for the details of visual scenes

Many studies suggest a large capacity memory for briefly presented pictures of whole scenes. At the same time, visual working memory (WM) of scene elements is limited to only a few items. We examined the role of retroactive interference in limiting memory for visual details. Participants viewed a scene for 5?s and then, after a short delay containing either a blank screen or 10 distracter scenes, answered questions about the location, color, and identity of objects in the scene. We found that the influence of the distracters depended on whether they were from a similar semantic domain, such as "kitchen" or "airport." Increasing the number of similar scenes reduced, and eventually eliminated, memory for scene details. Although scene memory was firmly established over the initial study period, this memory was fragile and susceptible to interference. This may help to explain the discrepancy in the literature between studies showing limited visual WM and those showing a large capacity memory for scenes.

Ordering the cytochrome c-initiated caspase cascade:hierarchical activation of caspases-2, -3, -6, -7, -8, and -10 in a caspase-9-dependent manner

Exit of cytochrome c from mitochondria into the cytosol has been implicated as an important step in apoptosis. In the cytosol, cytochrome c binds to the CED-4 homologue, Apaf-1, thereby triggering Apaf-1-mediated activation of caspase-9. Caspase-9 is thought to propagate the death signal by triggering other caspase activation events, the details of which remain obscure. Here, we report that six additional caspases (caspases-2, -3, -6, -7, -8, and -10) are processed in cell-free extracts in response to cytochrome c, and that three others (caspases-1, -4, and -5) failed to be activated under the same conditions. In vitro association assays confirmed that caspase-9 selectively bound to Apaf-1, whereas caspases-1, -2, -3, -6, -7, -8, and -10 did not. Depletion of caspase-9 from cell extracts abrogated cytochrome c-inducible activation of caspases-2, -3, -6, -7, -8, and -10, suggesting that caspase-9 is required for all of these downstream caspase activation events. Immunodepletion of caspases-3, -6, and -7 from cell extracts enabled us to order the sequence of caspase activation events downstream of caspase-9 and reveal the presence of a branched caspase cascade. Caspase-3 is required for the activation of four other caspases (-2, -6, -8, and -10) in this pathway and also participates in a feedback amplification loop involving caspase-9.

Blocking in children's causal learning depends on working memory and reasoning abilities.

A sample of 99 children completed a causal learning task that was an analogue of the food allergy paradigm used with adults. The cue competition effects of blocking and unovershadowing were assessed under forward and backward presentation conditions. Children also answered questions probing their ability to make the inference posited to be necessary for blocking by a reasoning account of cue competition. For the first time, children's working memory and general verbal ability were also measured alongside their causal learning. The magnitude of blocking and unovershadowing effects increased with age. However, analyses showed that the best predictor of both blocking and unovershadowing effects was children's performance on the reasoning questions. The magnitude of the blocking effect was also predicted by children's working memory abilities. These findings provide new evidence that cue competition effects such as blocking are underpinned by effortful reasoning processes.