High-temperature nanoindentation behavior of Al/SiC multilayers

Nanoscale Al/SiC composite laminates have unique properties, such as high strength, high toughness, and damage tolerance. In this article, the high-temperature nanoindentation response of Al/SiC nanolaminates is explored from room temperature up to 300°C. Selected nanoindentations were analyzed postmortem using focused ion beam and transmission electron microscopy to ascertain the microstructural changes and the deformation mechanisms operating at high temperature.     

Melting point depression method for determining the solid–liquid interfacial energy of metal elements: theoretical validation and updated compilation of data

Comparative analyses of the crystal nucleation method and the melting point depression (MPD) method for measuring the solid–liquid interface energy γ_sl are carried out. The MPD method is found more reliable and has several advantages from experiment through data analysis to theoretical generalisation. The MPD data in use, all reported before the 1970s, are updated with the derived γ_sl re-compiled. Finally, by invoking a melting model that we developed recently, an equation for calculating γ_sl is proposed on basis of the melting point depression method.     

The chemical potential and the work function of a metal film on a dielectric substrate

The chemical potential and the work function of an aluminium metal film which is in the vacuum (1) and on a dielectric substrate (2) are obtained using the model of non-interacting electrons confined by an asymmetric rectangular potential well. For the first time, these two characteristics are calculated with correct taking into account the electroneutrality condition. As a result, the values of the chemical potential and the work function tend to their bulk values upon increasing the film thickness. The presence of a dielectric substrate leads to a small shift in the values of these characteristics.     

Main and interaction effects of metallic toxins on aggressive classroom behavior

The present study investigated possible relationships of metal levels and metal combinations to children's aggressive classroom behavior. Hair-metal concentrations of lead, arsenic, mercury, cadmium, and aluminum were determined in 80 randomly selected elementary-age children. Each child was also rated by his classroom teacher on the acting-out subscale of the Walker Problem Behavior Identification Checklist. Parents of subjects were interviewed to control for confounding variables that may affect behavioral development. Regression data indicated that the set of metals was significantly related to increased scores on the acting-out subscale (P < 0.07) with lead being the major contributor (P < 0.05), and the metal combinations were also significantly related to increased acting-out scores (P < 0.01) with the interaction of lead-cadmium being the major contributor (P < 0.001). A continuing reexamination of metal-poisoning concentrations is needed, because metal levels and metal combinations previously thought harmless may be associated with aggressive classroom behavior.     

Eschewing Community: Black Metal

There is a great deal of literature that examines community orientations, in particular consumption‐based subcultures rooted in the appreciation of music scenes such as heavy metal and its subgenres. Much of this literature focuses on aspects of community maintenance, reaffirmation of shared identities and building of social bonds. In the present article, we report a study in which consumption of, and fandom in a specific scene in extreme metal, namely black metal, may lead to very unique consumer cultural orientations. Our analyses reveal that black metal fans' identities reside in a realm outside of a desired collective identification and tightly knit community, but rather one that uses signification, or representational means to convey meaning and belonging, as a way to signal repugnance with society and a reverence of individuality. The study engages a mixed qualitative approach utilizing interviews, observational research and content analysis to demonstrate how self‐identity related to the black metal music scene can thrive through an ideological and semiotic rejection of traditional community orientations seen in the majority of other extreme metal music scenes. This paper challenges traditional conceptualizations of group identity in music scenes by closely examining aspects of signification and fandom in black metal that represent a unique system of shared identities devoid of community building. Copyright © 2014 John Wiley & Sons, Ltd.     

Nanoindentation study of size effects in nickel–graphene nanocomposites

Metal–graphene nanocomposites find applications in nanoscale devices, as functional materials and can serve as a test bed to gain insight into fundamental deformation mechanisms of metals under geometric confinement. Here, we report full atomistic nanoindentation simulations for nickel–graphene nanocomposites with varied numbers of layers of graphene sheets to investigate the size effects on the hardness, and to understand how emerging dislocation loops interact with the nickel–graphene interface under varied geometric confinements. A detailed analysis of the plastic deformation mechanism shows that as dislocation loops reach the nickel–graphene interface, the local bending of the graphene sheet is altered and further dislocation propagation is blocked. An increase in the number of graphene layers decreases the hardness, but increases the maximum elastic deformation of the nickel–graphene nanocomposites. These findings indicate that the mechanical properties of nickel–graphene nanocomposites can be engineered by controlling the thickness of nickel and graphene layers, respectively.     

On the length scale of cyclic strain localization in fine-grained copper films

Fine-grained copper films on a flexible substrate were cyclically deformed under constant strain range control. It was found that cyclic dislocation plasticity through individual dislocation glide is still dominant at the submicrometer scale, while the ability of irreversible slip of dislocations gradually decreases and the damage was changed from extrusion-induced localization to cracking along grain boundary. Statistical evaluation of the mean spacing between slip bands and/or lines leads to a critical scale (～28 nm) below which dislocation-controlled cyclic strain localization would be shut down.     

Failure mode of isotropic three-dimensional reticulated porous materials under various compressive loads

The failure mode of isotropic three-dimensional reticulated porous materials under compression has been investigated. A mathematical relationship between nominal main stresses and porosity has been derived for this class of materials at shearing failure under various compressive loads from the simplified structural model of an octahedron. These compressive loads cover all three loading conditions, including uniaxial compression, biaxial compression and triaxial compression. The results indicate that (1) the failure mode is relative to the material species of these porous bodies under compression, (2) the porous body of brittle material species will show the tensile fracture mode of pore struts and (3) the porous body of ductile material species will probably display the shearing fracture mode of pore struts. Through a relevant expression, the criterion of strength design can be enhanced for these porous materials under shearing failure caused by compressive loadings.     

Heavy metal Muslims: the rise of a post-Islamist public sphere

This article explores the emergence of new, youth-oriented public spheres in the Middle East and North Africa through the lens of the burgeoning extreme music scenes across the region. I argue that the seeming incongruity of genres such as extreme heavy metal or gangsta rap becoming popular in the Muslim world is a reminder of the diversity of contemporary Islam; more deeply, it reveals that the borders between religious belief and seemingly secular practices in Muslim societies are increasingly porous, with politically marginalized young metalheads and their more activist religious peers sharing many of the same societal goals. These are greater autonomy and even democracy, the right for tolerance of divergent views, and the rejection of the hypocrisy, corruption and authoritarianism of their leaders. I conclude with an analysis of the political implications of a still tentative rapprochement between ostensibly secular artists and the religious forces who less than a decade ago were spearheading their persecution, and in some cases prosecution, across the region.     

全髋关节表面置换进展及若干问题的思考

全髋关节表面置换术与传统的全髋关节置换术相比有众多优点,然而随着研究的深入,全髋关节表面置换的缺点不断暴露,其中牵涉到很多矛盾的思想观点,如骨水泥在假体固定中的应用与否,髋臼臼杯变形与臼杯厚度、植入技术的复杂关系等。分析存在的矛盾且深入探索,从而发现解决矛盾的办法。