Large transport landing characteristics as simulated in flight and on the ground

Comparison of theoretical and simulated low speed landing characteristics for large transport aircraft

The effect of small-amplitude time-dependent changes to the surface morphology of a sphere

Typical approaches to manipulation of flow separation employ passive means or active techniques such as blowing and suction or plasma acceleration. Here it is demonstrated that the flow can be significantly altered by making small changes to the shape of the surface. A proof of concept experiment is performed using a very simple time-dependent perturbation to the surface of a sphere: a roughness element of 1% of the sphere diameter is moved azimuthally around a sphere surface upstream of the uncontrolled laminar separation point, with a rotational frequency as large as the vortex shedding frequency. A key finding is that the non-dimensional time to observe a large effect on the lateral force due to the perturbation produced in the sphere boundary layers as the roughness moves along the surface is ˆt =tU_(∞)/D ≈4. This slow development allows the moving element to produce a tripped boundary layer over an extended region. It is shown that a lateral force can be produced that is as large as the drag. In addition, simultaneous particle image velocimetry and force measurements reveal that a pair of counter-rotating helical vortices are produced in the wake, which have a significant effect on the forces and greatly increase the Reynolds stresses in the wake. The relatively large perturbation to the flow-field produced by the small surface disturbance permits the construction of a phase-averaged, three-dimensional (two-velocity component) wake structure from measurements in the streamwise/radial plane. The vortical structure arising due to the roughness element has implications for flow over a sphere with a nominally smooth surface or distributed roughness. In addition, it is shown that oscillating the roughness element, or shaping its trajectory, can produce a mean lateral force

Investigating the Effects That Alcohol Consumption has on the Impulse Buying Behaviors of College Students

This paper looks at the relationships between alcohol consumption and the impulse buying behaviors of college students. The first section of the study looks at what categories of products are most commonly purchased whilst each student is under the influence of alcohol. The criteria for classing something as an impulse purchase in this section is that you can’t have previously planned on buying the product, and/or you end up spending more than you initially intended, whilst you are under the influence. We found that food, more alcohol, and gifts for others were the top three categories in this section. The next section is comprised of 18 questions which have a possible answer range of 1 through 7. These are used to see how strongly each respondent agrees with each statement made about their behaviors surrounding alcohol and impulsive behaviors. Lastly, the number of drinks that the respondent consumes on average during a week, and also during a night out with friends, is recorded, along with whether they are an active member of a Fraternity or Sorority. The study found that heavy drinkers report more problems of impulsive overspending. After analyzing and discussing the results of the questions, and the possible relationships between drinking and impulse buying, the paper then looks at possible managerial implications of the information, and the limitations of this study, as well as ideas for future research

The role of extraterrestrial particles in the formation of the ozone hole. Part I: The concentration of extraterrestrial particles at ozone hole formation

The object of Part I of this paper is to estimate the concentration of extraterrestrial particles in the ozone layer over South Pole, Antarctica, during ozone hole formation. This estimate is based on an analysis of microscopic magnetic spherules collected in an extended program of atmospheric sampling. Spherules are shown to be of extraterrestrial origin and serve as markers for the larger class of less distinguished extraterrestrial particles. These particles settle to ground level as aggregates formed in a stratospheric ice crystal coalescence process. Specific spherule arrivals at ground level are strongly associated with apparent ozone depletion episodes during formation of the ozone hole. The origin of these spherules is a major stream of extraterrestrial particles independent of known meteor showers. The variability in its intensity from year to year corresponds to the variability in ozone depletion in the ozone hole itself. A quantitative theory based on these spherule arrivals and this coalescence process implies that the concentration of extraterrestrial particles at ozone hole formation lies between500 and 2000 / m3. A mechanism is proposed in Part II of this paper by which particle concentrations in this range are sufficient to produce the ozone hole

The role of extraterrestrial particles in the formation of the ozone hole. Part II: The action of extraterrestrial particles at ozone hole formation

The object of this paper is to assess the possibility that particles of extraterrestrial origin play a significant role in the formation of the ozone hole. Preliminary analysis shows that air in the ozone layer over South Pole tends to be stable, saturated, and essentially particle-free just prior to ozone hole formation. Further, gas-phase reactions generally responsible for ozone loss in the atmosphere are unrelated to ozone hole formation. According to Part I of this paper, a massive influx of extraterrestrial particles invades the ozone layer over South Pole precisely at ozone hole formation. We hypothesize that ozone diffuses to the surfaces of these particles, where it is adsorbed and enters into a series of reactions leading to its net loss in the atmosphere. To test this hypothesis, we have constructed a mathematical model of this process. We have also identified principal features in ozone hole formation in field data for 1986. These include the start of ozone hole formation three weeks before sunrise, a spike in ozone concentration at sunrise, and cessation in ozone depletion before disintegration of the circumpolar vortex. Projections of the model are in good agreement with these features. To conclude, this analysis has developed strong evidence that the ozone hole is primarily a natural phenomenon caused by the depletion of ozone in reactions on the surfaces of extraterrestrial particles

On Polyhedral Projection and Parametric Programming

This paper brings together two fundamental topics: polyhedral projection and parametric linear programming. First, it is shown that, given a parametric linear program (PLP), a polyhedron exists whose projection provides the solution to the PLP. Second, the converse is tackled and it is shown how to formulate a PLP whose solution is the projection of an appropriately defined polyhedron described as the intersection of a finite number of halfspaces. The input to one operation can be converted to an input of the other operation and the resulting output can be converted back to the desired form in polynomial time—this implies that algorithms for computing projections or methods for solving parametric linear programs can be applied to either problem clas

Reachability analysis of discrete-time systems with disturbances

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