Air-clad fibers: pump absorption assisted by chaotic wave dynamics?

Wave chaos is a concept which has already proved its practical usefulness in design of double-clad fibers for cladding-pumped fiber lasers and fiber amplifiers. In general, classically chaotic geometries will favor strong pump absorption and we address the extent of chaotic wave dynamics in typical air-clad geometries. While air-clad structures supporting sup-wavelength convex air-glass interfaces (viewed from the high-index side) will promote chaotic dynamics we find guidance of regular whispering-gallery modes in air-clad structures resembling an overall cylindrical symmetry. Highly symmetric air-clad structures may thus suppress the pump-absorption efficiency eta below the ergodic scaling law eta proportional to Ac/Acl, where Ac and Acl are the areas of the rare-earth doped core and the cladding, respectively.Comment: High-resolution figures and animations available in the freely available published version (click the DOI link

Utilization of Vehicle-Specific Power as a Powertrain Independent Platoon Controller Performance Metric

Heavy-Duty hauling faces challenges regarding the efficiency of transportation, which opens the door to new pathways to saving money while refueling via platooning. Platooning vehicles travel together intending to reduce aerodynamic resistance during operation. The increasing interest in autonomous solutions directs research toward applying these solutions to heavy-duty transportation. However, autonomous solutions are a relatively new concept and require significant research before implementation on public roads. This dilemma brings forth a new application of an emissions quantification metric called vehicle-specific power (VSP). VSP bridges the gap between passenger vehicle emissions rates and fuel consumption. VSP considers the total driving environment of a vehicle, which estimates powertrain effort to maintain current conditions. The present work utilizes the powertrain effort estimation aspect of VSP rather than its emissions investigative benefits to evaluate the efficacy of Cooperative Adaptive Cruise Control (CACC). Different controller strategies and platoon configurations are examined to determine the applicability of VSP to controller evaluation. Experimentation was completed at the National Center for Asphalt Technology (NCAT) circuitous track, the American Center for Mobility’s (ACM) freeway loop, and a straightaway section of NCAT’s track dubbed “ideal” for platooning efficiency. The influence of convoy position, following distance, road grade, speed, and acceleration are investigated via VSP. VSP aims to create a more complete cost function for assessing a controller’s strategy while implementing a forward-looking evaluation technique to current controller strategies. This cost function provides incredible insight into increasing the efficiency of an autonomously driven platoon

Heavy Meson Description with a Screened Potential

We perform a quark model calculation of the $b\bar{b}$ and $c\bar{c}$ spectra from a screened funnel potential form suggested by unquenched lattice calculations. A connection between the lattice screening parameter and an effective gluon mass directly derived from QCD is established. Spin-spin energy splittings, leptonic widths and radiative decays are also examined providing a test for the description of the states.Comment: 17 pages, no figures, to appear in Phys. Rev.