458 research outputs found
Dual-Mission Large Aircraft Feasibility Study and Aerodynamic Investigation
A Dual-Mission Large Aircraft, or DMLA, represents the possibility of a single aircraft capable of fulfilling both a Global Reach Aircraft (GRA) and Very Large Transport (VLT) roles. The DMLA, by combining the GRA and VLT into a single new aircraft, could possibly lower the aircraft manufacturer's production costs through the resulting increase in production quantity. This translates into lower aircraft acquisition costs, a primary concern for both the Air Force and commercial airlines. This report outlines the first steps taken in this study, namely the assessment of technical and economic feasibility of the DMLA concept. In the course of this project, specialized GRA and VLT aircraft were sized for their respective missions, using baseline conventional (i.e., lacking advanced enabling technologies) aircraft models from previous work for the Air Force's Wright Laboratory and NASA-Langley. DMLA baseline aircraft were then also developed, by first sizing the aircraft for the more critical of the two missions and then analyzing the aircraft's performance over the other mission. The resulting aircraft performance values were then compared to assess technical feasibility. Finally, the life-cycle costs of each aircraft (GRA, VLT, and DMLA) were analyzed to quantify economic feasibility. These steps were applied to both a two-engine aircraft set, and a four-engine aircraft set
Enhanced emission prediction modeling and analysis for conceptual design
Issued as final reportUnited States. National Aeronautics and Space Administratio
Advanced Design Methodology for Robust Aircraft Sizing and Synthesis
Contract efforts are focused on refining the Robust Design Methodology for Conceptual Aircraft Design. Robust Design Simulation (RDS) was developed earlier as a potential solution to the need to do rapid trade-offs while accounting for risk, conflict, and uncertainty. The core of the simulation revolved around Response Surface Equations as approximations of bounded design spaces. An ongoing investigation is concerned with the advantages of using Neural Networks in conceptual design. Thought was also given to the development of systematic way to choose or create a baseline configuration based on specific mission requirements. Expert system was developed, which selects aerodynamics, performance and weights model from several configurations based on the user's mission requirements for subsonic civil transport. The research has also resulted in a step-by-step illustration on how to use the AMV method for distribution generation and the search for robust design solutions to multivariate constrained problems
A Message Passing Strategy for Decentralized Connectivity Maintenance in Agent Removal
In a multi-agent system, agents coordinate to achieve global tasks through
local communications. Coordination usually requires sufficient information
flow, which is usually depicted by the connectivity of the communication
network. In a networked system, removal of some agents may cause a
disconnection. In order to maintain connectivity in agent removal, one can
design a robust network topology that tolerates a finite number of agent
losses, and/or develop a control strategy that recovers connectivity. This
paper proposes a decentralized control scheme based on a sequence of
replacements, each of which occurs between an agent and one of its immediate
neighbors. The replacements always end with an agent, whose relocation does not
cause a disconnection. We show that such an agent can be reached by a local
rule utilizing only some local information available in agents' immediate
neighborhoods. As such, the proposed message passing strategy guarantees the
connectivity maintenance in arbitrary agent removal. Furthermore, we
significantly improve the optimality of the proposed scheme by incorporating
-criticality (i.e. the criticality of an agent in its
-neighborhood).Comment: 9 pages, 9 figure
Improved Aircraft Environmental Impact Segmentation via Metric Learning
Accurate modeling of aircraft environmental impact is pivotal to the design
of operational procedures and policies to mitigate negative aviation
environmental impact. Aircraft environmental impact segmentation is a process
which clusters aircraft types that have similar environmental impact
characteristics based on a set of aircraft features. This practice helps model
a large population of aircraft types with insufficient aircraft noise and
performance models and contributes to better understanding of aviation
environmental impact. Through measuring the similarity between aircraft types,
distance metric is the kernel of aircraft segmentation. Traditional ways of
aircraft segmentation use plain distance metrics and assign equal weight to all
features in an unsupervised clustering process. In this work, we utilize
weakly-supervised metric learning and partial information on aircraft fuel
burn, emissions, and noise to learn weighted distance metrics for aircraft
environmental impact segmentation. We show in a comprehensive case study that
the tailored distance metrics can indeed make aircraft segmentation better
reflect the actual environmental impact of aircraft. The metric learning
approach can help refine a number of similar data-driven analytical studies in
aviation.Comment: 32 pages, 11 figure
Simulating Corrective Maintenance: Aggregating Component Level Maintenance Time Uncertainty at the System Level
AbstractThe corrective maintenance process can be decomposed into failure and repair processes. Creating a model to capture the corrective maintenance process then requires an accurate estimate of the behavior of these constituent processes. For systems composed of many individual parts, information about failure and repair behavior is more likely to be available at the component level than the system level. Depending on the number of components that comprise the system, modeling each part may become computationally burdensome; in addition, some few components may account for a large portion of the overall system failures.In such a situation, one solution to the modeling burden is aggregation: the mathematical assimilation of many component distributions into a single representative distribution for the group. This paper describes how aggregation may be performed for such a system and how an algorithm may be developed to automate the process. Next, it describes how to simulate an aggregated distribution using a pseudo-random number generator and finally demonstrates these concepts for a sample problem. The first section of the paper introduces corrective maintenance modeling and aggregation; the second section describes aggregation for corrective maintenance; the third explains how to simulate the aggregated distribution; the fourth demonstrates aggregation; and the fifth discusses limitations of the method and concludes
Integrating Equity into Health Information Systems: A Human Rights Approach to Health and Information
Health information systems can play a crucial role in supporting human rights by documenting and tracking health and health inequities, and by creating a platform for action and accountabilit
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