Superelastic NiTi honeycombs: fabrication and experiments

In this paper we demonstrate a new class of superelastic NiTi honeycomb structures. We have developed a novel brazing technique that has allowed us to fabricate Nitinol-based cellular structures with relative densities near 5%. Commercially available nickel-rich Nitinol strips were shape-set into corrugated form, stacked, and bonded at high temperature by exploiting a contact eutectic melting reaction involving pure niobium. After heat treatment to restore transformational superelastic response, prototype honeycomb structures were subjected to severe in-plane compression loading at room temperature. The specimens exhibited good specific strength, high specific stiffness, and enhanced shape recovery compared to monolithic shape memory alloys (SMAs). Compressive strains of over 50% could be recovered upon unloading. The demonstrated architectures are simple examples of a wide variety of possible built-up topologies, enabled by the bonding method, that can be engineered for customizable net section properties, arbitrary shape, and kinematically enhanced thermomechanical shape-memory and superelastic response.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58146/2/sms7_1_S17.pd

Low-density open-cell foams in the NiTi system

It is shown that open-cell metallic foams having very low density, and that display martensite transformations required for shape memory and superelastic behavior, can be fabricated using a powder-metallurgy technique. Results are presented on experiments in which a polymeric precursor foam was coated with an equiatomic NiTi powder slurry and subsequently sintered to yield foams with relative densities as low as 0.039. Although contaminated with interstitial impurities, they displayed unambiguous calorimetric signature of the B2→B19′B2→B19′ transformation. The results are of considerable significance to potential applications requiring ultralightweight structures with the unusual dissipative and strain-recovery properties of NiTi shape-memory materials. © 2003 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71336/2/APPLAB-82-16-2727-1.pd

Shape memory alloy honeycombs: experiments & simulation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76238/1/AIAA-2007-1739-156.pd

Health warning labels and alcohol selection: a randomised controlled experiment in a naturalistic shopping laboratory

Abstract: Background and aims: Health warning labels (HWLs) on tobacco products reduce smoking. There is an absence of evidence concerning the impact of alcohol HWLs on selection or purchasing in naturalistic settings. Using a commercial‐standard naturalistic shopping laboratory, this study aimed to estimate the impact on selection of alcoholic drinks of HWLs describing adverse health consequences of excessive alcohol consumption. Design: A between‐subjects randomised experiment with three groups was conducted: group 1: image‐and‐text HWL; group 2: text‐only HWL; group 3: no HWL. Setting: A commercial‐standard naturalistic shopping laboratory in the United Kingdom. Participants: Adults (n = 399, 55% female) over the age of 18 years, who purchased beer or wine weekly to drink at home. Interventions: Participants were randomised to one of three groups varying in the HWL displayed on the packaging of the alcoholic drinks: (i) image‐and‐text HWL (n = 135); (ii) text‐only HWL (n = 129); (iii) no HWL (n = 135). Participants completed a shopping task, selecting items from a range of alcoholic and non‐alcoholic drinks, and snacks. Measurement: The primary outcome was the proportion of alcoholic drinks selected. Secondary outcomes included HWL ratings on negative emotional arousal and label acceptability. Findings: There was no clear evidence of a difference in the HWL groups for the percentage of drinks selected that were alcoholic compared to no HWL (44%): image‐and‐text HWL: 46% (odds ratio [OR] = 1.08, 95% confidence interval [CI] = 0.82, 1.42); text‐only HWL: 41% (OR = 0.87, 95% CI = 0.67, 1.14). Concordant with there being no difference between groups, there was extreme evidence in favour of the null hypothesis (Bayes factor [BF] < 0.01). Negative emotional arousal was higher (P < 0.001) and acceptability lower (P < 0.001) in the image‐and‐text HWL group, compared to the text‐only HWL group. Conclusions: In a naturalistic shopping laboratory, there was no evidence that health warning labels describing the adverse health consequences of excessive alcohol consumption changed selection behaviour

Decision Making and Problems of Evidence for Emerging Educational Technologies

Appears as chapter 10 of the book The Best Available Evidence: Decision Making for Educational Improvement.With the ever-expanding range of emerging educational technologies that could be introduced to learning environments, making evidence-informed decisions about whether and how to effectively use e-learning tools for pedagogical purposes is a critical yet challenging task. How can educators, learners, and administrators make informed decisions about the use of particular emerging technologies to achieve desired pedagogical transformation when, due to their relative newness, there is often a perceived lack of available and “up-to-the-minute” research on the latest technological trends that may impede evidence-based educational practice? This is a key problem of evidence for technology use in higher education. This chapter discusses several exigent problems of evidence for decision making regarding emerging technologies, particularly for higher education, beginning with a brief overview of evidence-based practice (EBP) and twenty-first century learning. We reflect upon strategies that educational practitioners may employ when facing a perceived lack of up-to-date evidence to support their decision-making processes. By discussing strategies for identifying affordances and employing environmental scanning, we describe approaches for mitigating potential research gaps when considering use of emerging technologies within academic learning contexts

Superelasticity and Stability of a Shape Memory Alloy Hexagonal Honeycomb under In-plane Compression

International audienc

Adaptation to a landscape-scale mountain pine beetle epidemic in the era of networked governance: the enduring importance of bureaucratic institutions

Landscape-scale forest disturbance events have become increasingly common worldwide under the combined influences of climate change and ecosystem modification. The mountain pine beetle (Dendroctonus ponderosae) epidemic that swept through North American forests from the late 1990s through the early 2010s was one of the largest such disturbance events on record and triggered shocks to ecological and economic systems. We analyze the policy and governance responses to this event by focusing on three national forests in the state of Colorado and on the agency responsible for their management, the U.S. Forest Service. We found that the event triggered the formation of new hybrid agency/nonagency organizations that contributed both legitimacy and capacity to address the most immediate threats to human safety and infrastructure. Despite the use of a highly networked governance structure, longstanding U.S. Forest Service institutions continued to heavily influence the scope of the response and the means for implementing management activities. We detected relatively limited institutional response at the level of the agency as a whole, even as regional- and local-scale institutions within Colorado showed greater dynamism. Indeed, the changes to agency institutions that were detected were largely consistent with institutional change trajectories already in place prior to the epidemic. Our study points to the importance of institutional persistence and path dependence in limiting the latitude for adaptation to social and environmental shocks