9,958 research outputs found
Programming of inhomogeneous resonant guided wave networks
Photonic functions are programmed by designing the interference of local waves in inhomogeneous resonant guided wave networks composed of power-splitting elements arranged at the nodes of a nonuniform waveguide network. Using a compact, yet comprehensive, scattering matrix representation of the network, the desired photonic function is designed by fitting structural parameters according to an optimization procedure. This design scheme is demonstrated for plasmonic dichroic and trichroic routers in the infrared frequency range
PAH emission from Nova Cen 1986
The discovery of broad emission features between 3.2 and 3.6 microns were reported in the spectrum of Nova Cen 1986 (V842 Cen) some 300 days following outburst and remaining prominent for several months. The general characteristics of these features are similar to those attributed to polycyclic hydrocarbon (PAH) molecules in other dusty sources, although the relative strengths are different, and these observations provide the first clear evidence for molecular constituents other than graphite particles in the ejecta of novae
COTTON CULTIVAR, PLANTING, IRRIGATING, AND HARVESTING DECISIONS UNDER RISK
Producers in southwest Oklahoma lack adequate information about optimal planting decisions for cotton. This study uses a cotton growth simulation model to evaluate alternative cultivar, planting date, irrigation, and harvest choices. Effects of using information about soil moisture at reproduction and revenue loss at harvest in making cultivar and planting data decisions are evaluated. Using soil temperature information to plant at an early date produced high net revenue some years, but reduced mean net revenue and increased risk. Producers maximizing expected net revenue should plant a short-season cultivar in late May and use soil moisture information to schedule irrigation at reproduction.Crop Production/Industries,
The Magnetic Properties of Heating Events on High-Temperature Active Region Loops
Understanding the relationship between the magnetic field and coronal heating
is one of the central problems of solar physics. However, studies of the
magnetic properties of impulsively heated loops have been rare. We present
results from a study of 34 evolving coronal loops observed in the Fe XVIII line
component of AIA/SDO 94 A filter images from three active regions with
different magnetic conditions. We show that the peak intensity per unit
cross-section of the loops depends on their individual magnetic and geometric
properties. The intensity scales proportionally to the average field strength
along the loop () and inversely with the loop length () for a
combined dependence of . These loop properties are
inferred from magnetic extrapolations of the photospheric HMI/SDO line-of-sight
and vector magnetic field in three approximations: potential and two Non Linear
Force-Free (NLFF) methods. Through hydrodynamic modeling (EBTEL model) we show
that this behavior is compatible with impulsively heated loops with a
volumetric heating rate that scales as .Comment: Astrophysical Journal, in pres
Negative refractive index in coaxial plasmon waveguides
We theoretically show that coaxial waveguides composed of a metallic core, surrounded by a dielectric cylinder and clad by a metal outer layer exhibit negative refractive index modes over a broad spectral range in the visible. For narrow dielectric gaps (10 nm GaP embedded in Ag) a figure-of-merit of 18 can be achieved at λ_0 = 460 nm. For larger dielectric gaps the negative index spectral range extends well below the surface plasmon resonance frequency. By fine-tuning the coaxial geometry the special case of n = −1 at a figure-of-merit of 5, or n = 0 for a decay length of 500 nm can be achieved
Dynamic Fracture in Single Crystal Silicon
We have measured the velocity of a running crack in brittle single crystal
silicon as a function of energy flow to the crack tip. The experiments are
designed to permit direct comparison with molecular dynamics simulations;
therefore the experiments provide an indirect but sensitive test of interatomic
potentials. Performing molecular dynamics simulations of brittle crack motion
at the atomic scale we find that experiments and simulations disagree showing
that interatomic potentials are not yet well understood.Comment: 4 pages, 4 figures, 19 reference
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