Broadband electromagnetic cloaking in the microwaves and visible
In our recent article “Broadband electromagnetic cloaking of long
cylindrical objects” (to appear in Physical Review Letters) we have
shown how very simple metallic parallel-plate structures can be used to
cloak or, in other words, to make “invisible” e.g. cylindrical metallic
objects. Two designs are presented: one operating in the microwave
region and the other in the visible part of the electromagnetic
spectrum.
Operation of both structures is confirmed with numerical simulations and the microwave device is also realized and measured. The
results confirm that this new cloaking phenomenon can be realized with
very simple structures and the designed devices are shown to operate in
relatively wide frequency bands.
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BE11444
Scientists Solve Mystery of Glass Flow
A popular urban legend concerns the apparent flow of stained glass windows in medieval cathedrals. This problem is of critical importance for modern industrial glass, particularly the ultra-thin glass sheets used in liquid crystal displays (LCDs), where such flow can lead to unwanted dimensional changes during the LCD manufacturing process. In a newly published paper, “Nonequilibrium viscosity of glass” (Phys. Rev. B), a trio of scientists have conducted the first-ever thorough investigation of viscous flow at temperatures below the glass transition. They present major advances in the underlying theory of nonequilibrium viscosity, developing a new model which accounts for the full thermal history dependence of glass flow behavior. Using an internally designed beam bending apparatus capable of accurate viscosity measurements well below the glass transition, the authors present a detailed validation study of Corning’s EAGLE XG glass, the most popular glass used in today’s large-scale LCD televisions. The new theory unveils a striking relationship between the history-dependent viscosity of the glass at low temperatures and the high-temperature viscosity of the equilibrium melt.
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BTR1060BJ
Coiled Nanotubes
Carbon nanotubes are promising materials for the future. It would be
interesting to study what would happen when it is curved or coiled. In this
paper, we report that ring shaped nanotubes would behave differently than
straight ones. In our experiment, we investigate many rings with different
diameters using laser spectrum. We found that rings would show more peaks in
their spectra. The smaller, the more peaks. Usually graphene sheet have only
one peak in its Raman G band, when it is rolled up and forms a tube, there
would be two peaks in the G band. In our case, the tube is further rolled up
to form a ring and the number of peaks increases to six. This interesting
phenomenon may promote a deeper understanding of the mechanism of the spectrum
of carbon nanotubes and related materials like graphene and graphite.
Currently, we attribute the increasing of peak number with additional
curvature to the changes in electronic structures resulted by the residual
strain during the formation process of ring structures.
