An attempt is made to explain the observed torsional oscillations of an airscrew by means of the 'wake' theory. It is shown that the aerodynamic torsional damping becomes negative at certain blade angles and frequencies; the frequencies, or speeds, at which a single blade becomes unstable are shown to differ slightly from the critical frequencies of a multi-blade airscrew. At low incidences it ...

A probabilistic methodology to quantify the impact of geometric variability on compressor aerodynamic performance is presented. High-fidelity probabilistic models of geometric variability are derived using a principal-component analysis of blade surface measurements. This probabilistic blade geometry model is then combined with a compressible, viscous blade-passage analysis to estimate the impa...

Measurements of the structure and evolution of the tip vortex from a rotor in low-speed forward flight are presented. On the advancing blade spanwise flow on the pressure side of the blade is comparable in magnitude to the inflow. Core circumferential velocity profiles show multiple features during formation. Trajectories and peak core velocities of the tip-vortex during its formation on top of...

PURPOSE To evaluate if the use of BLADE sequences might overcome some limitations of magnetic resonance imaging (MRI) in the extracranial head and neck, which is a diagnostically challenging area with a variety of artifacts and a broad spectrum of potential lesions. MATERIALS AND METHODS After informed consent and Institutional Review Board approval, two different BLADE sequences with (BLADE ...

OBJECTIVE The purpose of this study was to compare two short-tau inversion recovery (STIR) sequences, Cartesian and radial (BLADE) acquisitions, for breast magnetic resonance imaging (MRI) examinations. MATERIALS AND METHODS Ninety-six women underwent 1.5 T breast MRI exam (48 Cartesian and 48 BLADE). Qualitative analysis including image artifacts, image quality, fat-suppression, chest-wall d...

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conclusion high-resolution mr images of the wrist using 3d t2space, pd blade and t2 blade were superior to those using conventional sequences quantitatively. high-snr and cnr mr imaging with space and blade would be a promising method to diagnose wrist lesions. results snr of the cartilage, tfcc on 3d t2space and t1 fse was better than other sequences (p < 0.001). snr of the bone on pd blade wa...

The Axial compressor is an integrated part of a gas turbine. The central part of compressors is its blades. Blade aerodynamic has a significant effect on compressor performance. Because of the adverse pressure gradient in the compressor, any deviation in the blade profile has a significant influence on the flow field as well as the compressor performance. During the manufacturing and operation ...

Iron oxide (Fe2O3) nanoparticles were prepared by combination of sol-gel autocombustion and ultrasonic irradiation. The XRD pattern reveals that the crystallite size of sample is 36.7 nm and the phase identification shows hematite, syn has been crystalized. The morphology of the sample investigated by FESEM showed that particle size of the sample was about 76 nm. The optic...