141 research outputs found
Consequences of an extirpation trial of the tree of heaven (ailanthus altissima (mill.) swingle) on rock grasslands and slope steppes
Giant microwave absorption in fine powders of superconductors
Enhanced microwave absorption, larger than that in the normal state, is
observed in fine grains of type-II superconductors (MgB and KC)
for magnetic fields as small as a few of the upper critical field. The
effect is predicted by the theory of vortex motion in type-II superconductors,
however its direct observation has been elusive due to skin-depth limitations;
conventional microwave absorption studies employ larger samples where the
microwave magnetic field exclusion significantly lowers the absorption. We show
that the enhancement is observable in grains smaller than the penetration
depth. A quantitative analysis on KC in the framework of the
Coffey--Clem (CC) theory explains well the temperature dependence of the
microwave absorption and also allows to determine the vortex pinning force
constant
Ultrafast sensing of photoconductivity decay using microwave resonators
Microwave reflectance probed photoconductivity (or -PCD) measurement
represents a contactless and non-invasive method to characterize impurity
content in semiconductors. Major drawbacks of the method include a difficult
separation of reflectance due to dielectric and conduction effects and that the
-PCD signal is prohibitively weak for highly conducting samples. Both of
these limitations could be tackled with the use of microwave resonators due to
the well-known sensitivity of resonator parameters to minute changes in the
material properties combined with a null measurement. A general misconception
is that time resolution of resonator measurements is limited beyond their
bandwidth by the readout electronics response time. While it is true for
conventional resonator measurements, such as those employing a frequency sweep,
we present a time-resolved resonator parameter readout method which overcomes
these limitations and allows measurement of complex material parameters and to
enhance -PCD signals with the ultimate time resolution limit being the
resonator time constant. This is achieved by detecting the transient response
of microwave resonators on the timescale of a few 100 ns \emph{during} the
-PCD decay signal. The method employs a high-stability oscillator working
with a fixed frequency which results in a stable and highly accurate
measurement.Comment: 7 pages, 6 figures+Supplementary Material
Smart Solutions for Guided Cultural Routes along the Iron Age Archaeological Sites of the Danube Basin
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