756 research outputs found

    Special Collection Editorial: grounded theory

    Get PDF

    Critical realism, agency and sickle cell: case studies of young people with sickle cell disorder at school

    Get PDF
    Critical realism suggests that historical structures may operate as underlying generative mechanisms but not always be activated. This explains the near-absence of references to racism by black students with sickle cell disorder (SCD). Through case studies we show how latent mechanisms are not activated, and how social actors come to develop corporate agency. Themes discussed include: wider/historical racisms (carers' own experiences of overt racism at school); conscious actions (moving away from a school where racism was experienced); naming racism as an emergent strategy (when communal discussions enable multiple negative experiences to be framed and named as racism); and `passing` (not ostensibly experiencing racism if one is sufficiently light-skinned). Critical realism suggests how racism may be structuring the experiences of students with SCD at school even in the absence of specific accounts by young people

    Turbine Electrified Energy Management (TEEM) For Enabling More Efficient Engine Designs

    Get PDF
    NASA is investing in Electrified Aircraft Propulsion (EAP) research as part of an effort to assist industry in meeting the future needs of a global aviation market. The integration of electric machines into traditional turbine-based propulsion provides opportunities to change system architectures effecting radical improvements in propulsive efficiency. However, less consideration has been afforded to the utilization of these electrical machines to improve the thermal efficiency and performance of the gas turbine engine. Noting this deficit, a novel operability concept is proposed and is referred to as Turbine Electrified Energy Management (TEEM). The concept is a transient control technology that supplements the main fuel control for the suppression of the natural off-design dynamics associated with changes in engine operating state. Here the electric machines, used as engine actuators during the transient, add or extract torque from the engine shafts to maintain the speed-flow characteristics of steady-state design operation. This greatly reduces the need to maintain transient stall margin stack in the compressors, among other potential benefits. This paper demonstrates the feasibility of the concept in dynamic simulation using a Numerical Propulsion System Simulation (NPSS) engine model of a NASA hybrid electric propulsion concept known as the Parallel Hybrid Electric Turbofan (hFan)

    Development of a Temperature Sensor for Jet Engine and Space Mission Applications

    Get PDF
    Electronics for Distributed Turbine Engine Control and Space Exploration Missions are expected to encounter extreme temperatures and wide thermal swings. In particular, circuits deployed in a jet engine compartment are likely to be exposed to temperatures well exceeding 150 C. To meet this requirement, efforts exist at the NASA Glenn Research Center (GRC), in support of the Fundamental Aeronautics Program/Subsonic Fixed Wing Project, to develop temperature sensors geared for use in high temperature environments. The sensor and associated circuitry need to be located in the engine compartment under distributed control architecture to simplify system design, improve reliability, and ease signal multiplexing. Several circuits were designed using commercial-off-the-shelf as well as newly-developed components to perform temperature sensing at high temperatures. The temperature-sensing circuits will be described along with the results pertaining to their performance under extreme temperature

    Development of a Temperature Sensor for Jet Engine and Space Missions Environments

    Get PDF
    Electronic systems in aerospace and in space exploration missions are expected to encounter extreme temperatures and wide thermal swings. To address the needs for extreme temperature electronics, research efforts exist at the NASA Glenn Research Center (GRC) to develop and evaluate electronics for extreme temperature operations, and to establish their reliability under extreme temperature operation and thermal cycling; conditions that are typical of both the aerospace and space environments. These efforts are supported by the NASA Fundamental Aeronautics/Subsonic Fixed Wing Program and by the NASA Electronic Parts and Packaging (NEPP) Program. This work reports on the results obtained on the development of a temperature sensor geared for use in harsh environments
    • …
    corecore