7,004 research outputs found

    Prediction, evaluation, and specification of flying qualities by means of step target tracking

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    A new approach to flying qualities specification and evaluation is presented which coordinates current research in the areas of pilot ratings, pilot-aircraft modeling techniques, and simulation and flight test procedures. A time-domain pilot model is described which can model discontinuous and nonlinear pilot behavior in conjunction with completely general time-varying nonlinear aircraft models to simulate discrete maneuvers. This pilot-aircraft model is applied to an existing set of in-flight simulation data, and calculates tracking error and time-on-target statistics for step target tracking that directly relate to the reported pilot comments and ratings. Predicted step target tracking data for eighteen F-5E flight conditions are presented, and the use of the method for control system design is demonstrated using the YF-17

    Prediction of pilot reserve attention capacity during air-to-air target tracking

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    Reserve attention capacity of a pilot was calculated using a pilot model that allocates exclusive model attention according to the ranking of task urgency functions whose variables are tracking error and error rate. The modeled task consisted of tracking a maneuvering target aircraft both vertically and horizontally, and when possible, performing a diverting side task which was simulated by the precise positioning of an electrical stylus and modeled as a task of constant urgency in the attention allocation algorithm. The urgency of the single loop vertical task is simply the magnitude of the vertical tracking error, while the multiloop horizontal task requires a nonlinear urgency measure of error and error rate terms. Comparison of model results with flight simulation data verified the computed model statistics of tracking error of both axes, lateral and longitudinal stick amplitude and rate, and side task episodes. Full data for the simulation tracking statistics as well as the explicit equations and structure of the urgency function multiaxis pilot model are presented

    Error rate information in attention allocation pilot models

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    The Northrop urgency decision pilot model was used in a command tracking task to compare the optimized performance of multiaxis attention allocation pilot models whose urgency functions were (1) based on tracking error alone, and (2) based on both tracking error and error rate. A matrix of system dynamics and command inputs was employed, to create both symmetric and asymmetric two axis compensatory tracking tasks. All tasks were single loop on each axis. Analysis showed that a model that allocates control attention through nonlinear urgency functions using only error information could not achieve performance of the full model whose attention shifting algorithm included both error and error rate terms. Subsequent to this analysis, tracking performance predictions for the full model were verified by piloted flight simulation. Complete model and simulation data are presented

    A qualitative perspective on multiple health behaviour change: views of smoking cessation advisors who promote physical activity

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    There are mixed views on whether smoking cessation advisors should focus only on quitting smoking or also promote simultaneous health behaviour changes (e.g. diet, physical activity), but no studies have qualitatively examined the views and vicarious experiences of such health professionals. Semi-structured interviews were conducted with 11 trained smoking cessation advisors who promote physical activity to their clients. The data were categorised into themes using thematic analysis supported by qualitative data analysis software. We report themes that were related to why advisors promote multiple health behaviour change and issues in timing. Physical activity could be promoted as a cessation aid and also as part of a holistic lifestyle change consistent with a non-smoker identity, thereby increasing feelings of control and addressing fear of weight gain. Multiple changes were promoted pre-quit, simultaneously and post-quit, and advisors asserted that it is important to focus on the needs and capabilities of individual clients when deciding how to time multiple changes. Also, suggesting that PA was a useful and easily performed cessation aid rather than a new behaviour (i.e. structured exercise that may seem irrelevant) may help some clients to avoid a sense of overload

    Psychosocial Correlates of Drug Use in Adolescents

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    The purpose of this study was to examine adolescent drug involvement in relation to a variety of psychological and social constructs. One hundred ninety-nine adolescent high school students and 67 adolescents receiving drug treatment served as subjects. A battery of questionnaires was administered to assess a participant’s: involvement with drugs (i.e., reported drug use index, intent to use drugs in the future, exposure to drugs, and level of drug use prior to abstinence); self-concept/self-esteem; social skills; and anxiety and depression levels. Degree of drug involvement, both within the student sample and between student and treatment samples, was related differentially to perceived psychological distress and perceived social competence. The measure most predictive of drug involvement in the student sample was the Social Avoidance and Distress Scale-suggesting that greater drug involvement is associated with greater levels of social anxiety. Additional analyses indicated that subjects less involved with drugs (i.e., abstinent and low-user student groups) tended to report less depression and anxiety and reported greater levels of self-concept/esteem and social competence (i.e., less social anxiety and less loneliness). The predictability of drug involvement by respondents was most accurate when all psychosocial measures, combined with selected sociodemographic variables were used

    ECONOMIC MODELING & OPTIMIZATION OF A REGION SPECIFIC MULTI-FEEDSTOCK BIOREFINERY SUPPLY CHAIN

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    The objective of this thesis is to include strategic and tactical level decisions into the biorefinery supply chain design for a specific region while comparing multiple conversion technologies and biomass feedstocks. The allocation of biomass feedstocks, products, and the respective supply chain configuration locations are determined while ensuring the regions monthly biomass availability and product market demand constraints are met. This research considers all actions required to bring the bio-based products to market from harvesting, storing, and processing the biomass to market distribution. Two different conversion technologies are chosen for comparison: one advanced conversion technology and one conventional technology. Potential investors and policy makers will be able to use this region specific tool by maximizing annual profitability to evaluate potential lignocellulosic biomass feedstocks and conversion technologies for the production of energy, fuels, and chemicals. The tool utilizes ILOG OPL software for optimization while interfacing with Microsoft Excel for parameter inputs and results output. From the sensitivity analysis, further insight is gained to what key drivers greatly influence the performance of each supply chain. The results demonstrate the practicality of this tool, which then can be further analyzed through other models such as discrete event simulation

    The anatomy and the histology of bud- formation in the serpulid Filograna implexa and with some cytological observations on the nuclei of the neoblasts

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    External Features • 1. General, 11 • 2. Phases of life history . 22 • 3. Configuration of buds . . 24 • 4. Grouping of segments considered numerically . . 36Description of two abnormal buds , 55Alimentary canal , . 58Body wall • 1. Epithelium , . . . 63 • 2. Musculature , . . . . . . 70 • 3. Central nervous system . . . . . 85Blood system . . . . . . 05Coelomic cavities . . . . 114Glandular sac and excretion. . . . 116Histology of bud -formation, together with cytological observations on the nuclei of the embryonic cells. 123.Summary. 152

    Risk communication in emergency response to a simulated extreme flood.

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    Risk communication in flood incident management can be improved through developing hydrometeorological and engineering models used as tools for communicating risk between scientists and emergency management professionals. A range of such models and tools was evaluated by participating flood emergency managers during a 4-day, real-time simulation of an extreme event in the Thamesmead area in the Thames estuary close to London, England. Emergency managers have different communication needs and value new tools differently, but the indications are that a range of new tools could be beneficial in flood incident management. Provided they are communicated large model uncertainties are not necessarily unwelcome among flood emergency managers. Even so they are cautious about sharing the ownership of weather and flood modelling uncertainties

    Body temperature manipulation and exercise performance in athletically trained males

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    Exercise or activity in high ambient temperatures offers a particular challenge to the thermoregulatory system. It is likely that mechanisms such as sweat evaporation alone are not sufficient for maintaining body temperature within a safe limit (~36.5-38.5ËšC) and below 40ËšC, which may result in impaired physiological function and performance. Exogenous cooling may be of benefit prior to, during and after events that place increased thermal strain due to increased metabolic heat production and elevated environmental temperatures upon the thermoregulatory system. Conversely, in situations where it is not possible to maintain body temperature via either continued physical activity or elevated ambient temperatures, exogenous heating may be required in order to allow optimal physiological performance. Few studies have directly aligned cooling devices with data detailing effective target regions for cooling to allow a pre-cooling garment to be of minimal weight but maximal cooling efficiency. Conversely, no study has considered the effect of muscle temperature maintenance during rest periods on subsequent power-based activities. The aim of this thesis was to determine ways in which body temperature manipulation is capable of improving exercise performance in both power and endurance-based events. It was hypothesised that the manipulation of body temperature will result in subsequent changes in body temperature that would improve performance. Specifically, the use of pre-cooling would result in a reduction of body temperature and improve endurance exercise performance. Conversely, maintaining Tm following warm up completion would have a beneficial effect on sprint and power related performance. Study one set out to determine differences in regional body heat loss in 12 individual anatomical zones using a water perfused suit. Data obtained from this initial study allowed for the specific targeting of regions that were identified as having high rates of heat loss in subsequent studies that focused on pre-cooling and performance. The anatomical regions identified as having high potential affinity for heat exchange with the surrounding environment and cooling devices were the hands, forearms, upper and lower back and torso. Subsequent studies demonstrated that cooling of these areas was capable of lowering thermal sensation and improving thermal comfort prior to and during exercise in moderate environmental conditions (24ËšC, 50% RH). In these moderate conditions, there was no statistically significant improvement in treadmill based self-paced 5000m running performance. However, in hot conditions (35ËšC 50% RH), the use of a cooling vest and sleeves did yield a significant improvement in cycling time trial performance, which equated to 4.8%. This leads to the suggestion that there may be a threshold ambient temperature, above which pre-cooling becomes an important tool in maximizing performance potential. A parallel area of investigation, on the other side of the temperature spectrum, was the effect of muscle temperature manipulation on power-based exercise performance. The relationship between increased muscle temperature and power output is well established, however little is known about the effect of enforced rest or recovery between two bouts of exercise. Therefore, two studies were conducted to establish what affect a delay between warm up completion and exercise has on muscle temperature and subsequent sprint cycling performance. It was shown that with 30-minutes of rest between exercise bouts wearing tracksuit trousers, muscle temperature declined significantly (~1-1.5ËšC). This decline was attenuated with the use of external passive electrical heating during the recovery compared to recovery completed in tracksuit trousers alone. The attenuated decline in muscle temperature following the use of the heated trousers resulted in an improvement in sprint cycling performance (~9%), with the use of insulated trousers having no effect on any variables measured, all relative to wearing tracksuit trousers in the rest period. In a follow-up study, the effect of implementing the heated trousers during the warm up and in addition to the rest period had on muscle temperature increase and sprint performance. A secondary area of investigation in this study was to determine the linearity of muscle temperature decline following warm up cessation. This study demonstrated that there was no additional benefit of combining passive heating with an active warm up on either muscle temperature elevations or subsequent sprint performance compared to the active warm up alone. It was shown that when the no heating was used at any stage, muscle temperature declined exponentially. However, when the heated trousers were used during recovery and/or during warm up, muscle temperature levelled off at a higher value towards the end of the recovery period. This study was also able to show significant improvements in absolute, relative and mean power output following the use of the heated trousers in the warm up and recovery, or the recovery alone. This thesis has identified ways in which body temperature may be manipulated in order to benefit both sprint and endurance exercise performance, using both pre-cooling and active heating. A novel concept for minimizing muscle temperature decline during periods of inactivity between different rounds of competition was shown to maximize sprint performance yielding significant improvements in peak and mean power outputs
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