55,545 research outputs found
Designed-in molecular interactions lead to superior thermo-mechanical properties in nanocomposites
The effect of the nanofiller chemistry on the mechanical behaviour of thermoset polymer matrix nanocomposites is investigated. The interaction between a crosslinked polymer resin and the reinforcing nanofibers driven by their chemistry is revealed by molecular dynamics simulations. Specifically, crosslinked network systems of neat epoxy and epoxy-P(St-co-GMA) are modeled to discuss the effect of various molecular interactions as a function of temperature on a molecular basis. At 433 K, incorporation of single molecule of bonded P(St-co-GMA) and nonbonded P(St-co-GMA) lead to increase in Young’s modulus by 10% and 6%, respectively,
compared to neat epoxy system
Modulational-instability-free pulse compression in anti-resonant hollow-core photonic crystal fiber
Gas-filled hollow-core photonic crystal fiber (PCF) is used for efficient
nonlinear temporal compression of femtosecond laser pulses, two main schemes
being direct soliton-effect self-compression, and spectral broadening followed
by phase compensation. To obtain stable compressed pulses, it is crucial to
avoid decoherence through modulational instability (MI) during spectral
broadening. Here we show that changes in dispersion due to spectral
anti-crossings between the fundamental core mode and core wall resonances in
anti-resonant-guiding hollow-core PCF can strongly alter the MI gain spectrum,
enabling MI-free pulse compression for optimized fiber designs. In addition,
higher-order dispersion can introduce MI even when the pump pulses lie in the
normal dispersion region
Volume 12, Number 8 - June 1932
Volume 12, Number 8 – June 1932. 30 pages including covers and advertisements. Ryan, Edward P. St. Albert the Scientist Meister, Joseph C. St. Albert the Philosopher Cleary, John J. St. Albert the Man of Public Affair Cap and Gown Day Exercises Harrison, Gordon F. Some Die Upon the Field Hackett, James M. I Like Gibbs Editorials Shunney, Walter J. Critique Haylon, William D. Checkerboard Sullivan for Tebbetts Athletic
Multipliers and Wiener-Hopf operators on weighted L^p spaces
We study the operators T on the weighted space L^p commuting either with the
right translations St or left translations P^+S_{-t} and we establish the
existence of a symbol of T. We characterize completely the spectrum of St. We
obtain a similar result for the spectrum of P^+S_{-t} and some spectral results
for the bounded operators commuting with (St), t>0 or with (P^+St), t<0
Nonlinear optics in Xe-filled hollow-core PCF in high pressure and supercritical regimes
Supercritical Xe at 293 K offers a Kerr nonlinearity that can exceed that of
fused silica while being free of Raman scattering. It also has a much higher
optical damage threshold and a transparency window that extends from the UV to
the infrared. We report the observation of nonlinear phenomena, such as
self-phase modulation, in hollow-core photonic crystal fiber filled with
supercritical Xe. In the subcritical regime, intermodal four-wave-mixing
resulted in the generation of UV light in the HE12 mode. The normal dispersion
of the fiber at high pressures means that spectral broadening can clearly
obtained without influence from soliton effects or material damage
Transformation Optics with Photonic Band Gap Media
We introduce a class of optical media based on adiabatically modulated,
dielectric-only, and potentially extremely low-loss, photonic crystals. The
media we describe represent a generalization of the eikonal limit of
transformation optics (TO). The foundation of the concept is the possibility to
fit frequency isosurfaces in the k-space of photonic crystals with elliptic
surfaces, allowing them to mimic the dispersion relation of light in
anisotropic effective media. Photonic crystal cloaks and other TO devices
operating at visible wavelengths can be constructed from optically transparent
substances like glasses, whose attenuation coefficient can be as small as 10
dB/km, suggesting the TO design methodology can be applied to the development
of optical devices not limited by the losses inherent to metal-based, passive
metamaterials.Comment: 4 pages, 4 figure
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