1,461 research outputs found

    Implications of control technology on aircraft design

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    New controls technologies are now available for implementation with aircraft systems. Many aircraft with state of the art technology in the fields of aerodynamics, structures, and propulsion require extensive augmentation merely for safety of flight considerations in addition to potential performance improvements. The actual performance benefits of integrating the new controls concepts with other new technologies is optimized by including such considerations early in the design process. Recently, several advanced aircraft designs have run into considerable problems related to control systems and flying qualities during flight test, requiring costly redesign and fine tuning efforts. It is no longer possible for the aircraft design to be completed prior to getting the control specialists involved. The challenge to the control system designer has become so great that his concerns must be considered at the conceptual design level. A computer program developed at NASA for evaluating the economic payoffs of integrating controls into the design of transport aircraft at the beginning will be described

    Experiences performing conceptual design optimization of transport aircraft

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    Optimum Preliminary Design of Transports (OPDOT) is a computer program developed at NASA Langley Research Center for evaluating the impact of new technologies upon transport aircraft. For example, it provides the capability to look at configurations which have been resized to take advantage of active controls and provide and indication of economic sensitivity to its use. Although this tool returns a conceptual design configuration as its output, it does not have the accuracy, in absolute terms, to yield satisfactory point designs for immediate use by aircraft manufacturers. However, the relative accuracy of comparing OPDOT-generated configurations while varying technological assumptions has been demonstrated to be highly reliable. Hence, OPDOT is a useful tool for ascertaining the synergistic benefits of active controls, composite structures, improved engine efficiencies and other advanced technological developments. The approach used by OPDOT is a direct numerical optimization of an economic performance index. A set of independent design variables is iterated, given a set of design constants and data. The design variables include wing geometry, tail geometry, fuselage size, and engine size. This iteration continues until the optimum performance index is found which satisfies all the constraint functions. The analyst interacts with OPDOT by varying the input parameters to either the constraint functions or the design constants. Note that the optimization of aircraft geometry parameters is equivalent to finding the ideal aircraft size, but with more degrees of freedom than classical design procedures will allow

    OPDOT: A computer program for the optimum preliminary design of a transport airplane

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    A description of a computer program, OPDOT, for the optimal preliminary design of transport aircraft is given. OPDOT utilizes constrained parameter optimization to minimize a performance index (e.g., direct operating cost per block hour) while satisfying operating constraints. The approach in OPDOT uses geometric descriptors as independent design variables. The independent design variables are systematically iterated to find the optimum design. The technical development of the program is provided and a program listing with sample input and output are utilized to illustrate its use in preliminary design. It is not meant to be a user's guide, but rather a description of a useful design tool developed for studying the application of new technologies to transport airplanes

    A description of an automated database comparison program

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    An interactive FORTRAN computer comparison program designed to automatically locate regions of incongruity between two databases is described. The software, guided by user input parameters, incrementally compares the databases and generates plots of these regions in the databases which do not compare within a specified tolerance. Additionally, tools are provided within the software which enable the user to statistically reduce the number of data points in the databases compared. To facilitate the description of these tools, the procedures used to compare two aerodynamic databases for an F-18A fighter aircraft are detailed

    Simulation model of a twin-tail, high performance airplane

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    The mathematical model and associated computer program to simulate a twin-tailed high performance fighter airplane (McDonnell Douglas F/A-18) are described. The simulation program is written in the Advanced Continuous Simulation Language. The simulation math model includes the nonlinear six degree-of-freedom rigid-body equations, an engine model, sensors, and first order actuators with rate and position limiting. A simplified form of the F/A-18 digital control laws (version 8.3.3) are implemented. The simulated control law includes only inner loop augmentation in the up and away flight mode. The aerodynamic forces and moments are calculated from a wind-tunnel-derived database using table look-ups with linear interpolation. The aerodynamic database has an angle-of-attack range of -10 to +90 and a sideslip range of -20 to +20 degrees. The effects of elastic deformation are incorporated in a quasi-static-elastic manner. Elastic degrees of freedom are not actively simulated. In the engine model, the throttle-commanded steady-state thrust level and the dynamic response characteristics of the engine are based on airflow rate as determined from a table look-up. Afterburner dynamics are switched in at a threshold based on the engine airflow and commanded thrust

    What you know can influence what you are going to know (especially for older adults)

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    Stimuli related to an individual's knowledge/experience are often more memorable than abstract stimuli, particularly for older adults. This has been found when material that is congruent with knowledge is contrasted with material that is incongruent with knowledge, but there is little research on a possible graded effect of congruency. The present study manipulated the degree of congruency of study material with participants’ knowledge. Young and older participants associated two famous names to nonfamous faces, where the similarity between the nonfamous faces and the real famous individuals varied. These associations were incrementally easier to remember as the name-face combinations became more congruent with prior knowledge, demonstrating a graded congruency effect, as opposed to an effect based simply on the presence or absence of associations to prior knowledge. Older adults tended to show greater susceptibility to the effect than young adults, with a significant age difference for extreme stimuli, in line with previous literature showing that schematic support in memory tasks particularly benefits older adults

    Perfectionism and achievement goals in young Finnish ice-hockey players aspiring to make the Under-16 national team

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    Research on perfectionism suggests that is it useful to differentiate between perfectionistic strivings and perfectionistic concerns. Regarding the 2 x 2 achievement goal framework, the usefulness of this differentiation was recently demonstrated in a study with university student athletes (Stoeber, Stoll, Pescheck, & Otto, 2008, Study 2), in which it was found that perfectionistic strivings were associated with mastery-approach and performance-approach goals and perfectionistic concerns with mastery-avoidance, performance-approach, and performance-avoidance goals. Because the study was largely exploratory and only used non-elite athletes, the aim of the present research was to replicate and extend these findings by investigating a sample of 138 young, elite ice-hockey players, while adding further measures of perfectionism and using structural equation modelling (SEM) to confirm the relationships between perfectionistic strivings, perfectionistic concerns,and the 2 x 2 achievement goals. The SEM results showed that, in elite athletes also, perfectionistic strivings are associated with mastery-approach and performance-approach goals, whereas perfectionistic concerns are associated with masteryavoidance, performance-approach, and performance-avoidance goals. Our findings corroborate the importance of differentiating between perfectionistic strivings and perfectionistic concerns when studying perfectionism in sports, because only perfectionistic concerns (and not perfectionistic strivings) are associated with maladaptive patterns of achievement goals

    The initial measurement structure of the Home Drinking Assessment Scale (HDAS)

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    Aims: To evaluate the initial psychometric properties of a novel Home Drinking Assessment Scale (HDAS). Participants: Five-hundred and twenty-five (58% female) participants recruited from the internet address book of an English University. This also included a sub-sample (6%) recruited from Twitter and Facebook contacts. Design and methods: Internet-based survey analysed using a two-stage factor analysis protocol and internal consistency(IC) assessment. Findings: A power calculation was made on the basis of pilot data and this established that 317 interviewees were required to test the reliability of the HDAS. The items comprising the HDAS were found to offer the best fit to data when they comprised two-subscales: (1) emotional reasons for home drinking (5-items) and (2) practical reasons for home drinking (3-items). Subscale 1 was also found to have acceptable IC whereas subscale 2 exhibited sub-optimal IC characteristics. Conclusions: This initial study indicates that the HDAS has promise as a measure of the individuals' rationale for home drinking. Subscale 1, may usefully be used in future research whereas the IC characteristics of subscale 2 suggests that further development is required, including the evaluation of additional items
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