11,288 research outputs found
Characterization and Dynamic Analysis of Long-Cavity Multi-Section Gain-Levered Quantum-Dot Lasers
This research investigates the impact of different device architectures on the frequency response of long-cavity multi-section quantum-dot lasers. This work focused on a novel 8.3-mm multi-section quantum-dot device which possessed the flexibility to be configured either as a single- or multi-section device having gain-to-modulation section ratios of 14:2 and 15:1. The long-cavity device design facilitated the testing of increased gain-to-modulation section length ratios previously unexplored in the context of the gain-lever effect. The investigation of the gain-lever effect showed improvements to both the modulation efficiency and modulation bandwidth of the device under test. The modulation efficiency and modulation bandwidth were found to vary as the modulation section length was increased, leading to the conclusion of an ideal gain-to-modulation section ratio. In addition to providing a means to investigate the gain-lever effect, the long-cavity quantum-dot device exhibited passive mode locking both with and without a saturable absorber present. While the predictable gain-lever effects were observed, long-cavity and mode-locking effects were also present in the response; these effects presented unexpected characteristics that are not captured by current published models
Reconsidering the One Leptoquark solution: flavor anomalies and neutrino mass
We reconsider a model introducing a scalar leptoquark to explain recent deviations from the standard model in
semileptonic decays. The leptoquark can accommodate the persistent tension
in the decays as long as its mass is
lower than approximately , and we show that a sizeable Yukawa
coupling to the right-chiral tau lepton is necessary for an acceptable
explanation. Agreement with the measured rates is mildly compromised for parameter choices addressing the
tensions in , where the model can significantly reduce the
discrepancies in angular observables, branching ratios and the
lepton-flavor-universality observables and . The leptoquark can
also reconcile the predicted and measured value of the anomalous magnetic
moment of the muon and appears naturally in models of radiative neutrino mass
derived from lepton-number violating effective operators. As a representative
example, we incorporate the particle into an existing two-loop neutrino mass
scenario derived from a dimension-nine operator. In this specific model, the
structure of the neutrino mass matrix provides enough freedom to explain the
small masses of the neutrinos in the region of parameter space dictated by
agreement with the anomalies in , but
not the transition. This is achieved without excessive fine-tuning in
the parameters important for neutrino mass.Comment: 43 pages, 17 figures, 3 tables; corrected fit contours in fig. 1
A simulation study of the flight dynamics of elastic aircraft. Volume 1: Experiment, results and analysis
The simulation experiment described addresses the effects of structural flexibility on the dynamic characteristics of a generic family of aircraft. The simulation was performed using the NASA Langley VMS simulation facility. The vehicle models were obtained as part of this research. The simulation results include complete response data and subjective pilot ratings and comments and so allow a variety of analyses. The subjective ratings and analysis of the time histories indicate that increased flexibility can lead to increased tracking errors, degraded handling qualities, and changes in the frequency content of the pilot inputs. These results, furthermore, are significantly affected by the visual cues available to the pilot
A simulation study of the flight dynamics of elastic aircraft. Volume 2: Data
The simulation experiment described addresses the effects of structural flexibility on the dynamic characteristics of a generic family of aircraft. The simulation was performed using the NASA Langley VMS simulation facility. The vehicle models were obtained as part of this research project. The simulation results include complete response data and subjective pilot ratings and comments and so allow a variety of analyses. The subjective ratings and analysis of the time histories indicate that increased flexibility can lead to increased tracking errors, degraded handling qualities, and changes in the frequency content of the pilot inputs. These results, furthermore, are significantly affected by the visual cues available to the pilot
Think-tanking the challenges in three regions: The Colorado Plateau
Unique features of the Colorado Plateau include aridity and the associated importance of water, topographic control on local ecosystems, large urban centers on the periphery but none within the region, and a combination of resource-extraction industries and tourism. Potential constraints to EM are conflicts in the legislative and administrative framework, inadequate staffing and funding of the agencies, insufficient communication among elements of the public, and the difficulty of achieving large number of monitoring and research sites, abundance of data, grass-roots ties to the land, and agency commitment. Needs for implementation are definition of EM, implementation initiated at the local level, and an atmosphere of trust and open communication
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