18,125 research outputs found

    Demonstrative Maneuvers for Aircraft Agility Predictions

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    This study was motivated by a need to develop a reliable method of predicting the agility characteristics of various aircraft. To fully investigate the agility of an aircraft, maneuvers which push the limits of an aircraft’s maneuvering capabilities must be simulated. In these cases, classic trajectory optimization techniques either require too many assumptions for a realistic solution or require a good guess of the final solution before the problem is even attempted. This study investigated both the utility of pseudospectral optimization methods for robust trajectory optimization as well as the potential for demonstrating differences in aircraft agility characteristics of several specific maneuvers. Building off of a pseudospectral optimization software package named DIDO, a robust maneuver definition and trajectory optimization system was developed to simulate various maneuvers specifically designed to demonstrate aircraft maneuvering limits. This system was used to optimize the trajectories of three variations of a baseline F-16 mathematical model developed to simulate important differences in aircraft agility characteristics. Initial results showed significant instabilities in the interface between the mathematical model and the optimization scheme. These instabilities were mitigated through modifications of the system’s cost function and the resulting trajectories demonstrated the relative advantages which can be created by subtle differences in aircraft designs. Future work in this area should include further refinement of the driving cost function and creation of a graphical user interface to simplify the maneuver definition process. The resulting system could be highly useful in other trajectory optimization research as well as non-related areas such as accident investigation and reverse engineering

    EXPORT ENHANCEMENT STRATEGIES FOR SMALL AND MEDIUM RURAL AND AGRICULTURAL FIRMS

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    Literature reports that small and medium firms face greater difficulty in obtaining the necessary export market information and in obtaining financing than do larger firms. Accordingly, the United States has many export promotion and enhancement services, but there is little documentation on the impacts of these services on small and medium rural and agricultural firms. The objectives of this project were to 1) analyze the export assistance needs of small and medium rural and agricultural firms operating in the Northern Plains region at different stages of the export or internationalization process, 2) identify available export assistance and promotion services offered at the federal and state levels to meet the needs of these firms, and 3) identify factors that may increase the effectiveness of export assistance programs. The primary assistance these firms wanted from the government was help in documenting their exports. The primary reasons firms did not seek government assistance were a lack of knowledge of the service and the service is not useful. The most often used non-government information sources were trade or industry associations and banks. Accordingly, policy makers should emphasize programs that complement efforts of private organizations and that target the needs and interests of the firms.export, rural, agriculture, export assistance, Northern Plains, government, Community/Rural/Urban Development, International Development,

    Activation of mammalian Chk1 during DNA replication arrest: a role for Chk1 in the intra-S phase checkpoint monitoring replication origin firing

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    Checkpoints maintain order and fidelity in the cell cycle by blocking late-occurring events when earlier events are improperly executed. Here we describe evidence for the participation of Chk1 in an intra-S phase checkpoint in mammalian cells. We show that both Chk1 and Chk2 are phosphorylated and activated in a caffeine-sensitive signaling pathway during S phase, but only in response to replication blocks, not during normal S phase progression. Replication block–induced activation of Chk1 and Chk2 occurs normally in ataxia telangiectasia (AT) cells, which are deficient in the S phase response to ionizing radiation (IR). Resumption of synthesis after removal of replication blocks correlates with the inactivation of Chk1 but not Chk2. Using a selective small molecule inhibitor, cells lacking Chk1 function show a progressive change in the global pattern of replication origin firing in the absence of any DNA replication. Thus, Chk1 is apparently necessary for an intra-S phase checkpoint, ensuring that activation of late replication origins is blocked and arrested replication fork integrity is maintained when DNA synthesis is inhibited

    PPA Printer Software Driver Design The software driver for the HP DeskJet 820C printer performs many

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    functions that were formerly performed in the printer, including swath cutting, data formatting, and communications. The driver also includes a PCL emulation module for DOS application support

    Washington Correlator

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    This report summarizes the activities of the Washington Correlator for 2012. The Washington Correlator provides up to 80 hours of attended processing per week plus up to 40 hours of unattended operation, primarily supporting Earth Orientation and astrometric observations. In 2012, the major programs supported include the IVS-R4, IVS-INT, APSG, and CRF observing sessions
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