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Evolution of microstructure and hardness in AZ31 alloy processed by high pressure torsion
Strá,ská,, Jitka,Janeč,ek, Miloš,Gubicza, Jenő,Krajň,á,k, Tomá,š,Yoon, Eun Yoo,Kim, Hyoung Seop Elsevier 2015 Materials science & engineering. properties, micro Vol.625 No.-
<P><B>Abstract</B></P> <P>A commercial MgAlZn alloy (AZ31) was processed by high pressure torsion (HPT) at room temperature, resulting in an extreme microstructure refinement down to the grain size of 150–250nm. The microstructure evolution during HPT was investigated by transmission electron microscopy and X-ray diffraction line profile analysis. The microhardness was measured as a function of the distance from the center of the disk and the number of HPT revolutions. The detailed analysis of dislocation contrast factors in X-ray diffraction line profiles enables to determine the population of the different slip systems as a function of the imposed strain. The influence of microstructure and defect structure evolution on microhardness is discussed in detail.</P>
Estrustura sint?ctica y constituyentes internos en espanol
Tomás Jiménez Juliá 한국스페인어문학회 2005 스페인어문학 Vol.0 No.37
La lengua es un sistema de comunicación que se basa en gran medida en la rentabilidad de sus medios. Por ello, suele omitir toda aquella información que el contexto pueda aportar y que, por tanto, haga superflua su expresión explícita. Dentro de las omisiones existen dos tipos fundamentales: la elipsis y la elisión. La primera tiene un carácter sistemático y tiene como fin destacar lo no omitido. La segunda busca primariamente la economía de medios, y tienen un carácter coyuntural o convencional. Dentro de las elisiones convencionales hay algunas que tienen su origen en el valor consabido de un cierto complemento, esto es, de los que denominamos ‘constituyentes internos’. Habitualmente se han reconocido como constituyentes internos solamente los ‘acusativos’. El presente artículo tiene como fin describir otros constituyentes internos, además de los acusativos, que normalmente no se reconocen como tales.
SPATIAL CLUSTERING FROM<i>GALEX</i>-SDSS SAMPLES: STAR FORMATION HISTORY AND LARGE-SCALE CLUSTERING
Heinis, Sé,bastien,Budavá,ri, Tamá,s,Szalay, Alex S.,Arnouts, Sté,phane,Aragó,n-Calvo, Miguel A.,Wyder, Ted K.,Barlow, Tom A.,Foster, Karl,Peter, Friedman G.,Martin, D. C IOP Publishing 2009 The Astrophysical journal Vol.698 No.2
Kang, Seoung-Hun,Kwon, Young-Kyun,Tomá,nek, David IOP Pub 2010 Journal of physics, an Institute of Physics journa Vol.22 No.50
<P>Using first principles density functional theory, we investigate the structural, electronic and magnetic properties of isolated and bundled Mo<SUB>6</SUB>S<SUB>9 − <I>x</I></SUB>I<SUB><I>x</I></SUB> nanowires with <I>x</I> = 3, 4.5, and 6. The unit cell of each system contains two Mo<SUB>6</SUB> octahedra decorated with S and I atoms and two S<SUB>3</SUB> linkages. Due to the bistability of each sulfur linkage, finite-length nanowires or nanowire bundles exhibit many stable structural minima. We explore the structural stability, elastic behavior and electronic structure at all these minima for each composition <I>x</I>. We find that the axial strain and inter-wire interaction in bundles significantly modify the electronic structure. The most intriguing changes occur in nanowires with <I>x</I> = 4.5 and 6, which change from metal to semiconductor or undergo a magnetic transition upon axially stretching or compressing the nanowires or upon changing the inter-wire separation. </P>
Park, Sora,Kittimanapun, Kritsada,Ahn, Jeung Sun,Kwon, Young-Kyun,Tomá,nek, David IOP Pub 2010 Journal of Physics, Condensed Matter Vol.22 No.33
<P>We use <I>ab initio</I> density functional calculations to study the stability, elastic properties and electronic structure of sp<SUP>2</SUP> carbon minimal surfaces with negative Gaussian curvature, called schwarzites. We focus on two systems with cubic unit cells containing 152 and 200 carbon atoms, which are metallic and very rigid. The porous schwarzite structure allows for efficient and reversible doping by electron donors and acceptors, making it a promising candidate for the next generation of alkali ion batteries. We identify schwarzite structures that act as arrays of interconnected spin quantum dots or become magnetic when doped. We introduce two interpenetrating schwarzite structures that may find their use as the ultimate super-capacitor. </P>
The effect of copper pre-cleaning on graphene synthesis
Kim, Soo Min,Hsu, Allen,Lee, Yi-Hsien,Dresselhaus, Mildred,Palacios, Tomá,s,Kim, Ki Kang,Kong, Jing IOP Pub 2013 Nanotechnology Vol.24 No.36
<P>Copper foil is the most common substrate to synthesize monolayer graphene by chemical vapor deposition (CVD). The surface morphology and conditions of the copper foil can be very different depending on the various suppliers or different batches. These surface properties of copper strongly affect the growth behavior of graphene, thus rendering the growth conditions irreproducible when different batches of Cu foil are used. Furthermore, the quality of the graphene is severely affected as well. In this work, we report a facile method of copper pre-cleaning to improve the graphene quality and the reproducibility of the growth process. We found that the commercial Ni etchant (based on nitric acid) or nitric acid is the most effective cleaning agent among various acidic or basic solutions. The graphene grown on thus-treated copper surfaces is very clean and mostly monolayer when observed under scanning electron microscopy (SEM) and optical imaging, as compared to the graphene grown on untreated copper foil. Different batches (but with the same catalog number) of copper foil from Alfa Aesar Company were examined to explore the effect of copper pre-cleaning; consistent growth results were obtained when pre-cleaning was used. This method overcomes a commonly encountered problem in graphene growth and could become one of the standard protocols for preparing the copper foil substrate for growing graphene or other 2D materials.</P>