1,008 research outputs found
Assessment of the application of advanced technologies to subsonic CTOL transport aircraft
Design studies of the application of advanced technologies to future transport aircraft were conducted. These studies were reviewed from the perspective of an air carrier. A fundamental study of the elements of airplane operating cost was performed, and the advanced technologies were ranked in order of potential profit impact. Recommendations for future study areas are given
Anderson Localization in a String of Microwave Cavities
The field distributions and eigenfrequencies of a microwave resonator which
is composed of 20 identical cells have been measured. With external screws the
periodicity of the cavity can be perturbed arbitrarily. If the perturbation is
increased a transition from extended to localized field distributions is
observed. For very large perturbations the field distributions show signatures
of Anderson localization, while for smaller perturbations the field
distribution is extended or weakly localized. The localization length of a
strongly localized field distribution can be varied by adjusting the
penetration depth of the screws. Shifts in the frequency spectrum of the
resonator provide further evidence for Anderson localization.Comment: 7 pages RevTex, to be published in Phys. Rev.
Wave Dynamical Chaos in a Superconducting Three-Dimensional Sinai Billiard
Based on very accurate measurements performed on a superconducting microwave
resonator shaped like a desymmetrized three-dimensional (3D) Sinai billiard, we
investigate for the first time spectral properties of the vectorial Helmholtz,
i.e. non-quantum wave equation for a classically totally chaotic and
theoretically precisely studied system. We are thereby able to generalize some
aspects of quantum chaos and present some results which are consequences of the
polarization features of the electromagnetic waves.Comment: 4 pages RevTex; 4 postscript figures; to be published in Phys. Rev.
Lett.; Info: [email protected]
A PLASIMO global model for plasma assisted CO2 conversion
Conversion of CO2 has become a major challenge of our time as it is of interest for the reduction of greenhouse gases in our atmosphere, but also to store energy thereby relieving the supply and demand discrepancy of many alternative forms of energy. Plasma assisted CO2 conversion is heavily investigated as an efficient method to achieve this goal. Numerical modeling is an important aspect of this investigation, but is difficult due to the complex chemistry. A global model has been constructed to focus on the CO2 chemistry including its vibrational kinetics. The model has been realized using the global model module of PLASIMO, a highly modular plasma modeling framework. It is based on another model\footnote{Tom\'{a}\v{s} Koz\'{a}k and Annemie Bogaerts, submitted to Plasma Sources Sci. Tech.} that was constructed using the well-established code Global\_kin. The aim of the model is therefore twofold. First, to study the chemistry and identify the most important species and reactions and perform parametric studies. The knowledge gained can be applied to other, spatially resolved models. Second, by implementing the same chemistry in the two different global model codes, a cross validation can be performed, a vital scientific process often overlooked in practice
A corner reflector of graphene Dirac fermions as a phonon-scattering sensor
Dirac fermion optics exploits the refraction of chiral fermions across
optics-inspired Klein-tunneling barriers defined by high-transparency p-n
junctions. We consider the corner reflector (CR) geometry introduced in optics
or radars. We fabricate Dirac fermion CRs using bottom-gate-defined barriers in
hBN-encapsulated graphene. By suppressing transmission upon multiple internal
reflections, CRs are sensitive to minute phonon scattering rates. We report on
doping-independent CR transmission in quantitative agreement with a simple
scattering model including thermal phonon scattering. As a new signature of
CRs, we observe Fabry-P\'erot oscillations at low temperature, consistent with
single-path reflections. Finally, we demonstrate high-frequency operation which
promotes CRs as fast phonon detectors. Our work establishes the relevance of
Dirac fermion optics in graphene and opens a route for its implementation in
topological Dirac matter.Comment: 11 pages, 4 figure
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