4,815 research outputs found
Pilot workload and fatigue: A critical survey of concepts and assessment techniques
The principal unresolved issues in conceptualizing and measuring pilot workload and fatigue are discussed. These issues are seen as limiting the development of more useful working concepts and techniques and their application to systems engineering and management activities. A conceptual analysis of pilot workload and fatigue, an overview and critique of approaches to the assessment of these phenomena, and a discussion of current trends in the management of unwanted workload and fatigue effects are presented. Refinements and innovations in assessment methods are recommended for enhancing the practical significance of workload and fatigue studies
Study of flight management requirements during SST low visibility approach and landing operations Final summary report
Flight management operational problems and task requirements for low visibility approach and landing of supersonic transport
Study of flight management requirements during SST low visibility approach and landing operations. Volume 2 - Delineation of potential problems in supporting the performance of flight management tasks
Potential flight management problems during low visibility landing of supersonic transport
Study of flight management requirements during SST low visibility approach and landing operations. Volume 1 - Definition of baseline SST landing system
Baseline instrument landing system for low visibility approach and landing of supersonic transport
Stochastic Yield Catastrophes and Robustness in Self-Assembly
A guiding principle in self-assembly is that, for high production yield,
nucleation of structures must be significantly slower than their growth.
However, details of the mechanism that impedes nucleation are broadly
considered irrelevant. Here, we analyze self-assembly into finite-sized target
structures employing mathematical modeling. We investigate two key scenarios to
delay nucleation: (i) by introducing a slow activation step for the assembling
constituents and, (ii) by decreasing the dimerization rate. These scenarios
have widely different characteristics. While the dimerization scenario exhibits
robust behavior, the activation scenario is highly sensitive to demographic
fluctuations. These demographic fluctuations ultimately disfavor growth
compared to nucleation and can suppress yield completely. The occurrence of
this stochastic yield catastrophe does not depend on model details but is
generic as soon as number fluctuations between constituents are taken into
account. On a broader perspective, our results reveal that stochasticity is an
important limiting factor for self-assembly and that the specific
implementation of the nucleation process plays a significant role in
determining the yield
Improving Forage Production on Claypan Soils
Mechanical range improvement practices such as contour ripping and furrowing have been used to increase forage production on a variety of range sites in the northern Great Plains. These improvement practices seem to have particular promise on Claypan and Thin Claypan range sites in western South Dakota. Soils on these range sites have a sodium dispersed layer (claypan) at or near the surface. This layer severely reduces the rate of water infiltration, thus causing a greater amount of the precipitation to run off or pool up and evaporate from the soil surface than would happen on soils of similar texture without the claypan layer. Because more precipitation water is lost to runoff and evaporation, less water is available for plant growth. The compact nature of the claypan layer also tends to restrict root growth, further reducing plant growth. Thus, claypan soils are inherently lower in forage production potential than similar soils without the claypan layer. The difference between productivity of the claypan soils and normal soils represents the potential increase in forage production if the effects of the claypan layer could somehow be removed
Polarons in semiconductor quantum-dots and their role in the quantum kinetics of carrier relaxation
While time-dependent perturbation theory shows inefficient carrier-phonon
scattering in semiconductor quantum dots, we demonstrate that a quantum kinetic
description of carrier-phonon interaction predicts fast carrier capture and
relaxation. The considered processes do not fulfill energy conservation in
terms of free-carrier energies because polar coupling of localized quantum-dot
states strongly modifies this picture.Comment: 6 pages, 6 figures, accepted for publication in Phys.Rev.
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UK Research Information Shared Service (UKRISS) Final Report, July 2014
The reporting of research information is a complex and expensive activity for research organisations (ROs). There is little alignment between funders of the reporting requests made to institutions and requests made to individual researchers about their research outputs and outcomes. This inevitably results in duplication and increased costs across the sector, whilst limiting the potential sharing and reuse of the information. The UK Research Information Shared Service (UKRISS) project conducted a feasibility and scoping study for the reporting of research information at a national level based on CERIF (Common European Research Information Format), with the objective of increasing efficiency, productivity and quality across the sector. The aim was to define and prototype solutions which are compelling, easy to use, have a low entry barrier, and support innovative information sharing and benchmarking. CERIF has emerged as the preferred format for expressing research information across Europe. To date, CERIF has been piloted for specific applications, but not as a format for reporting requirements across all UK ROs. The final report presents the work carried out by the UKRISS project, including requirements gathering, modelling and prototyping, as well as recommendation for sustainability. UKRISS was divided into two phases. Phase 1, mapping the reporting landscape, ran from March 2012 to December 2012. Phase 2, exploring delivery of potential solutions, began in February 2013 and ended in December 2013
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