817 research outputs found
On Silicides in High Temperature Titanium Alloys
High temperature titanium alloys like IMI 685 contain small amounts of silicon (~ 0.25 wt. per cent) to improve creep resistance. Different types of silicides, namely Ti5Si3 (TiZr)5Si3(S1) and (TiZr)6 Si3 (S2), have been observed to precipitate in various silicon-bearing titanium alloys depending upon their composition and heat treatment. The precipitation of silicides, their orientation relationship with the matrix in different alloys, and the beneficial influence of thermo-mechanical treatment on the distribution of silicides have been pointed out. The effect of silicides on mechanical properties and fracture of the commercial alloy IMI 685 is also indicated
Undercooling studies on dispersed bismuth droplets
In the zinc-bismuth system, a monotectic reaction occurs at 689 K and 0·6 at.% Bi composition. Rapid solidification of the as-cast monotectic alloy led to a micromorphology in which bismuth was uniformly and bimodally distributed as small droplets in the zinc matrix. Statistical analysis of the electron micrographs obtained from different transparent regions of the foils revealed that the size of most of the droplets was about 6 nm. These droplets undercooled by 132 K. An analysis of the nucleation rate measurements shows that the activation energy barrier to nucleation is of the order of 39·8 kcal/mol at the maximum undercooling
Tunable hybrid surface waves supported by a graphene layer
We study surface waves localized near a surface of a semi-infinite dielectric
medium covered by a layer of graphene in the presence of a strong external
magnetic field. We demonstrate that both TE-TM hybrid surface plasmons can
propagate along the graphene surface. We analyze the effect of the Hall
conductivity on the disper- sion of hybrid surface waves and suggest a
possibility to tune the plasmon dispersion by the magnetic field.Comment: 3 pages, 3 figure
Saving transatlantic cooperation and the Iran nuclear deal: a view from Europe and the United States
Transatlantic differences over the future of the Iran nuclear deal - or the Joint Comprehensive Plan of Action (JCPOA) of July 2015 - are damaging a nuclear accord that all parties, except the United States, see as delivering on its purpose. They also increase the risk of Washington and European capitals working at cross-purposes vis-à-vis Iran and broader regional policies. To avoid such a scenario, the E3 (France, Germany, United Kingdom)/European Union (EU) and the United States need to set up new channels of communication to avoid a transatlantic rift, to attempt - if at all possible - to preserve the Iran deal, and to secure its benefits for regional and global security. (author's abstract
Triaxial projected shell model study of gamma-vibrational bands in even-even Er isotopes
We expand the triaxial projected shell model basis to include
triaxially-deformed multi-quasiparticle states. This allows us to study the
yrast and gamma-vibrational bands up to high spins for both gamma-soft and
well-deformed nuclei. As the first application, a systematic study of the
high-spin states in Er-isotopes is performed. The calculated yrast and
gamma-bands are compared with the known experimental data, and it is shown that
the agreement between theory and experiment is quite satisfactory. The
calculation leads to predictions for bands based on one- and two-gamma phonon
where current data are still sparse. It is observed that gamma-bands for
neutron-deficient isotopes of 156Er and 158Er are close to the yrast band, and
further these bands are predicted to be nearly degenerate for high-spin states.Comment: 6 pages, 9 figure
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