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Effects of nonlinear aerodynamics and static aeroelasticity on mission performance calculations for a fighter aircraft

During conceptual design studies of advanced aircraft, the usual practice is to use linear theory to calculate the aerodynamic characteristics of candidate rigid (nonflexible) geometric external shapes. Recent developments and improvements in computational methods, especially computational fluid dynamics (CFD), provide significantly improved capability to generate detailed analysis data for the use of all disciplines involved in the evaluation of a proposed aircraft design. A multidisciplinary application of such analysis methods to calculate the effects of nonlinear aerodynamics and static aeroelasticity on the mission performance of a fighter aircraft concept is described. The aircraft configuration selected for study was defined in a previous study using linear aerodynamics and rigid geometry. The results from the previous study are used as a basis of comparison for the data generated herein. Aerodynamic characteristics are calculated using two different nonlinear theories, potential flow and rotational (Euler) flow. The aerodynamic calculations are performed in an iterative procedure with an equivalent plate structural analysis method to obtain lift and drag data for a flexible (nonrigid) aircraft. These static aeroelastic data are then used in calculating the combat and mission performance characteristics of the aircraft

Competitive abilities and ecological impacts of Tamarix aphylla in southern Nevada

Tamarix aphylla, an evergreen tree that hybridizes with the more widespread deciduous shrub T. ramosissima, has invaded the drawdown zone of Lake Mead in the southwestern U.S. To determine the ecological impacts and the invasive potential of T. aphylla, vegetative and soil characteristics of habitats dominated by either T. aphylla or T. ramosissima were measured, and competition experiments between T. aphylla and T. ramosissima , and between T. aphylla and the native Salix gooddingii were performed. Stands of both Tamarix species were similar in density and cover of vegetation, with each species tending to have higher density and cover values at one of the two sites measured. Tamarix aphylla plants were significantly taller than T. ramosissima, and tended to have larger basal diameters and canopies. Salinity was significantly higher in soils collected under the canopy of T. aphylla than in soils collected under T. ramosissima, whereas soil total Kjeldahl nitrogen, pH, and organic matter in soil varied between species by site. In the competition experiments, increases in T. aphylla density had a greater negative effect on relative growth rates of both T. aphylla and the native S. gooddingii when the two species were paired. However, T. ramosissima had a greater negative effect on the relative growth rate of both Tamarix species when the two species were paired. Because of the competitive abilities and ecological impacts of T. aphylla, action should be taken to ensure that this plant does not further invade riparian ecosystems in the southwestern U.S

Horace Greeley, Presidential Candidate: A Floridian\u27s View

In the presidential election of 1872, Horace Greeley, editor of the New York Tribune, was the candidate of the Liberal Republican Party and of the Democratic Party. Nominated first by the Liberal Republicans at their convention in Cincinnati, Greeley had been named by the Democrats at Baltimore in July, 1872. The Democrats not only adopted the candidate of the Liberal Republicans but also adopted their platform verbatim