363 research outputs found
Invariant imbedding theory of mode conversion in inhomogeneous plasmas. II. Mode conversion in cold, magnetized plasmas with perpendicular inhomogeneity
A new version of the invariant imbedding theory for the propagation of
coupled waves in inhomogeneous media is applied to the mode conversion of high
frequency electromagnetic waves into electrostatic modes in cold, magnetized
and stratified plasmas. The cases where the external magnetic field is applied
perpendicularly to the direction of inhomogeneity and the electron density
profile is linear are considered. Extensive and numerically exact results for
the mode conversion coefficients, the reflectances and the wave electric and
magnetic field profiles inside the inhomogeneous plasma are obtained. The
dependences of mode conversion phenomena on the magnitude of the external
magnetic field, the incident angle and the wave frequency are explored in
detail.Comment: 11 figures, to be published in Physics of Plasma
Electromagnetic modes of Maxwell fisheye lens
We provide an analysis of the radial structure of TE and TM modes of the
Maxwell fisheye lens, by means of Maxwell equations as applied to the fisheye
case. Choosing a lens of size R = 1 cm, we plot some of the modes in the
infrared range.Comment: 2+6 pages in Latex, 3 figures to be found in the published referenc
Theory of the propagation of coupled waves in arbitrarily-inhomogeneous stratified media
We generalize the invariant imbedding theory of the wave propagation and
derive new invariant imbedding equations for the propagation of arbitrary
number of coupled waves of any kind in arbitrarily-inhomogeneous stratified
media, where the wave equations are effectively one-dimensional. By doing this,
we transform the original boundary value problem of coupled second-order
differential equations to an initial value problem of coupled first-order
differential equations, which makes the numerical solution of the coupled wave
equations much easier. Using the invariant imbedding equations, we are able to
calculate the matrix reflection and transmission coefficients and the wave
amplitudes inside the inhomogeneous media exactly and efficiently. We establish
the validity and the usefulness of our results by applying them to the
propagation of circularly-polarized electromagnetic waves in one-dimensional
photonic crystals made of isotropic chiral media. We find that there are three
kinds of bandgaps in these structures and clarify the nature of these bandgaps
by exact calculations.Comment: 7 pages, 1 figure, to appear in Europhys. Let
RoboCup 2D Soccer Simulation League: Evaluation Challenges
We summarise the results of RoboCup 2D Soccer Simulation League in 2016
(Leipzig), including the main competition and the evaluation round. The
evaluation round held in Leipzig confirmed the strength of RoboCup-2015
champion (WrightEagle, i.e. WE2015) in the League, with only eventual finalists
of 2016 competition capable of defeating WE2015. An extended, post-Leipzig,
round-robin tournament which included the top 8 teams of 2016, as well as
WE2015, with over 1000 games played for each pair, placed WE2015 third behind
the champion team (Gliders2016) and the runner-up (HELIOS2016). This
establishes WE2015 as a stable benchmark for the 2D Simulation League. We then
contrast two ranking methods and suggest two options for future evaluation
challenges. The first one, "The Champions Simulation League", is proposed to
include 6 previous champions, directly competing against each other in a
round-robin tournament, with the view to systematically trace the advancements
in the League. The second proposal, "The Global Challenge", is aimed to
increase the realism of the environmental conditions during the simulated
games, by simulating specific features of different participating countries.Comment: 12 pages, RoboCup-2017, Nagoya, Japan, July 201
Justification for meso-scale modelling in quantifying constraint during creep crack growth
Broadside radar echoes from ionized trails
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77210/1/AIAA-2347-553.pd
Quiet daytime Arctic ionospheric D region
Phase and amplitude measurements of VLF radio waves propagating sub‐ionospherically on long paths across the Arctic are used to determine the high latitude, daytime D region height and sharpness of the bottom edge of the Earth's ionosphere. The principal path used is from the 23.4 kHz transmitter, DHO, in north Germany, northwards across the Arctic passing ~2° from the North Pole, and then southwards to Nome, Alaska, thus avoiding most land and all thick ice. Significant observational support is obtained from the also nearly all‐sea path from JXN in Norway (~67° N, 16.4 kHz) across the North Pole to Nome. By suitably comparing measurements with modeling using the US Navy code LWPC, the daytime D region (Wait) height and sharpness parameters in the Arctic are found to be H' = 73.7 ± 0.7 km and ß = 0.32 ±0.02 km‐1 in the summer of 2013 ‐ i.e., at (weak) solar maximum. It is also found that, unlike at lower latitudes, VLF phase and amplitude recordings on (~1000 km) paths at high subarctic latitudes show very little change with solar zenith angle in both phase and amplitude during daytime for solar zenith angles ~300 keV for electrons) with a contribution from galactic cosmic rays, rather than by solar Lyman‐α which dominates at low and middle latitudes
Implementation of the World's largest measles-rubella mass vaccination campaign in Bangladesh: a process evaluation
Background: Gavi, the Vaccine Alliance, supported a mass vaccination Measles-Rubella Campaign (MRC) in Bangladesh during January–February 2014
Aza-Cibalackrot: Turning on Singlet Fission Through Crystal Engineering
Singlet fission is a photophysical process that provides a pathway for more efficient harvesting of solar energy in photovoltaic devices. The design of singlet fission candidates is non-trivial and requires careful optimization of two key criteria: (1) correct energetic alignment and (2) appropriate intermolecular coupling. Meanwhile, this optimization must not come at the cost of molecular stability or feasibility for device applications. Cibalackrot is a historic and stable organic dye which, although it has been suggested to have ideal energetics, does not undergo singlet fission due to large interchromophore distances, as suggested by single crystal analysis. Thus, while the energetic alignment is satisfactory, the molecule does not have the desired intermolecular coupling. Herein, we improve this characteristic through molecular engineering with the first synthesis of an aza-cibalackrot and show, using ultrafast transient spectroscopy, that singlet fission is successfully "turned on.
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