2,363 research outputs found

    Hydraulic manipulator design, analysis, and control at Oak Ridge National Laboratory

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    The 24th Aerospace Mechanisms Symposium

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    The proceedings of the symposium are reported. Technological areas covered include actuators, aerospace mechanism applications for ground support equipment, lubricants, latches, connectors, and other mechanisms for large space structures

    Advanced sensors technology survey

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    This project assesses the state-of-the-art in advanced or 'smart' sensors technology for NASA Life Sciences research applications with an emphasis on those sensors with potential applications on the space station freedom (SSF). The objectives are: (1) to conduct literature reviews on relevant advanced sensor technology; (2) to interview various scientists and engineers in industry, academia, and government who are knowledgeable on this topic; (3) to provide viewpoints and opinions regarding the potential applications of this technology on the SSF; and (4) to provide summary charts of relevant technologies and centers where these technologies are being developed

    Recent Progress in Some Aircraft Technologies

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    The book describes the recent progress in some engine technologies and active flow control and morphing technologies and in topics related to aeroacoustics and aircraft controllers. Both the researchers and students should find the material useful in their work

    Advances in Piezoelectric Systems: An Application-Based Approach.

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    Active load control techniques for wind turbines.

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    Semi-Passive Control Strategy using Piezoceramic Patches in Non Linear Commutation Architecture for Structural-Acoustic Smart Systems

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    The demands for novel smart damping materials can be summarized in: external power source not required for operation; device not needing to be tuned to a specific frequency; device operation not affected by changes in modal frequency; device suppressing vibration over a number of modes, weight and size minimized; self-contained unit device. This thesis focuses on these points and it shows that the dilemma between active and passive vibration control may be solved with a new approach, implementing a semipassive technique without penalties in terms of robustness and performance. Connecting a shunt circuit to a piezoelectric transducer leads to a simple and low cost vibration controller that is able to efficiently suppress unwanted structural vibrations: this is a way to fulfil the abovementioned demands. The objective of this work is to develop and validate by an experimental campaign a computational tool integrated with finite element Nastran software. An original 4-channel switched shunt control system has been realized using a tachometer device. The control system has been tested first of all on a simple cantilevered beam attaining a max vibrations reduction of 16.2 dB for the first bending mode. Further reference test article consisted of a 10 ply fibreglass laminate plate. A multimodal control has applied within a band range of 700Hz including the first seven modes. A maximum reduction of 16 dB has been found. Further numerical and experimental tests have been planned to extend the ability of the SSC to produce structural-borne sound reduction in acoustic rigid cavities for fluid-structure interaction problems. Numerical sound power radiation of an aluminium plate, controlled by synchronized switch system, compared with the experimental acoustic energy detected in acoustic room, has been planned in the ongoing activities

    Space Station Systems Technology Study. Volume 2: Trade study and technology selection technical report

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    High leverage technologies are examined for application to the space station. The areas under investigation include attitude control, data management, long life thermal management, and automated housekeeping integration

    Active Cancellation of Tollmien-Schlichting Waves under Varying Inflow Conditions for In-Flight Application

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    Active flow control in laminar boundary layers can reduce wall friction on a wing, if laminar-turbulent transition is delayed. In this thesis, (re-)active flow control for active cancellation of Tollmien-Schlichting (TS) waves in a two-dimensional laminar boundary layer is investigated. The TS-waves that initiate the transition to turbulence are attenuated with a DBD plasma actuator by superposition. Active wave cancelation requires the use of control algorithms and their stability is influenced by variable inflow conditions. Model-based (Linear-Quadratic-Gaussian) and adaptive control algorithms (filtered-x-LMS) are investigated under realistic (varying) inflow conditions in wind-tunnel and in-flight experiments. The further developed delayed-x-LMS algorithm allows a stable and robust controller operation for active wave cancelation in flight. All experimental results are validated by direct numerical simulations and linear stability theory. Furthermore, the challenges for the application of DBD plasma actuator arrays to delay natural transition are pointed out. The simplification of transfer paths for reducing the required computational power is discussed

    Device to dynamically stretch cells during microscopic visualization

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    Cells in physiological systems are constantly subjected to mechanical forces which affect myriad cellular functions and contribute to pathologies. Current devices to study cellular responses to strain in vitro have drawbacks including the inability to analyze cellular responses in “real-time”, non-uniform strains patterns, and limited operation time (\u3c6 hr). To overcome these limitations, a novel stretch device was developed using four linear motors and a novel silicone culture well. The device is capable of cyclic stretching of cells biaxially up to 30% strain in either or both of two orthogonal axes at 0.01 to 1 Hz frequency for a minimum of 6 hr during “real-time” analysis of cells under a standard inverted microscope. This new system will facilitate controlled mechanobiology studies
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