Showing papers by "Vaughn College of Aeronautics and Technology published in 2004"

Evaluating the potential impact of alternative airport pricing approaches on social welfare

Abstract: One of the key issues air transportation policy-makers face is whether it is preferable from a regulatory perspective for airports to adopt a single-till or dual-till pricing approach. This study analyzes the potential loss of social welfare as a result of adopting a single-till or dual-till approach in three airport pricing scenarios. Findings show that the single-till approach is preferable where excess capacity of aeronautical services exists, while the dual-till approach is preferable where capacity is fully utilized or already over-utilized. A single-till approach induces airports to bear financial losses from aeronautical services and subsequently a cross-subsidy by profits raised from non-aeronautical activities is required. The dual till-approach enables congested airports to break even on aeronautical service and pursue profits from non-aeronautical activities.

Shock-wave/boundary-layer interaction control using streamwise slots in transonic flows

Abstract: The effect of streamwise slots on the interaction of a normal shock wave with a turbulent boundary layer has been investigated experimentally at a Mach number of 1.29. The surface-pressure distribution for the controlled interaction was found to feature a distinct plateau. This was caused by a change in shock structure from a typical unseparated normal shock-wave/boundary-layer interaction to a large bifurcated lambda-type shock pattern, which led to a reduction of total pressure losses. A strong spanwise variation of boundary-layer properties was observed downstream of the slots, whereas the modified shock structure was relatively two-dimensional. Surface flow visualization confirmed that the slots introduced a region of recirculation into the boundary layer, similar to passive control with uniform surface ventilation. Surface flow visualization revealed the presence of a pair of counter-rotating vortices, confirmed by crossflow velocity measurements. Because of the reduction of total pressure losses, streamwise slots can reduce aircraft wave drag at transonic cruise while incurring only small viscous penalties. A similar control device can also be of use in supersonic intakes where total pressure losses limit engine performance

Study of variable stars in the MOA data base: long-period red variables in the Large Magellanic Cloud – II. Multiplicity of the period–luminosity relation

Abstract: Data for 4.4 million stars from the Microlensing Observations in Astrophysics (MOA) project are compared with the near-infrared data of the Deep Near Infrared Southern Sky Survey (DENIS). More than 4000 stars observed in both projects show a quite periodic light curve. Among them, a number of stars are likely eclipsing variables, and the others seem to be pulsating stars. The Ks magnitudes of these red variables are in the range 10-12.5 but a minor clump at K S 12.2 mag is also found. The multiplicity of the period-luminosity relation is confirmed, but most of the regular, large-amplitude variables are found on the relation established for the Mira stars. We study the properties of the variables on the colour-magnitude diagram constructed with the MOA red band R m and Ks of DENIS. Multiplicity of the period-luminosity relation is briefly discussed in relation to the excitation mechanism of red pulsating variables.

Composite thin films Fe:BaTiO3 grown on MgO(100) substrates

Abstract: Fe-doped barium titanate (BaTiO3) thin films with good surface morphology were fabricated on MgO(100) substrates using pulsed laser deposition. The target was a Fe/BaTiO3 two-material physical assembly. X-ray diffraction and atomic force microscopy were used to examine the crystalline property and surface roughness of the films, respectively. The results show that a little amount of iron can be doped into BaTiO3 films during the deposition process without destroying the crystal structure and surface morphology. The nonlinear optical properties of the films were determined using the Z-scan method at a wavelength of 532 nm. The obtained real and imaginary parts of the third-order nonlinear susceptibility x((3)) were 3.67 x 10(-7) esu and 4.82 x 10(-8) esu, respectively.