Here, we show that during their half-century history, helicopters have been evolving into geometrically similar architectures with surprisingly sharp correlations between dimensions, performance , and body size. For example, proportionalities emerge between body size, engine size, and the fuel load. Furthermore, the engine efficiency increases with the engine size, and the propeller radius is r...

This work proposes a feedback control strategy to let the dynamics of an underactuated Vertical Take-Off and Landing (VTOL) aerial vehicle to track a desired trajectory thanks to an adaptive robust compensation of the aerodynamic disturbances. The novelty of the proposed approach consists in employing an aerodynamic disturbance observer derived using the NonLinear Geometric Approach and Radial ...

A new propeller EPI pulse sequence with reduced sensitivity to field inhomogeneities is proposed. Image artifacts such as blurring due to Nyquist ghosting and susceptibility gradients are investigated and compared with those obtained in previous propeller EPI studies. The proposed propeller EPI sequence uses a readout that is played out along the short axis of the propeller blade, orthogonal to...

Sound-producing sand grains constitute one of nature’ s more puzzling and least understood physical phenomena. They occur naturally in two distinct types: booming and squeaking sands. Although both varieties of sand produce unexpectedly pure acoustic emissions when sheared, they diŒer in their frequency range and duration of emission, as well as the environment in which they tend to be found. L...

The physically correct capture of propeller-rudder interaction is important if ship self-propulsion parameters are to be accurately predicted. Full resolution of a time accurate computational fluid dynamics calculation based on the Reynolds Averaged Navier Stokes equations requires a significant computational resource. The axial and tangential accelerations generated in the flow by the passage ...

The demand for new propeller designs has increased alongside the development of technology, such as urban aircraft and large unmanned aerial vehicles. In order to experimentally identify performance a propeller, wind tunnel that provides operating flow is essential. However, in case meter class or larger required related equipment becomes heavy; therefore, it difficult implement reality. For th...

However, a solution does exist, whose understanding relies on the application of the classical laws of physics and which is free of contradictions: if the electron is assumed to be made up of two massless constituent particles, then this assumption correctly predicts the experimental results. It provides the correct relationship between the parameters of the electron: its mass, its constant ang...

An analysis was conducted to examine the market visibility of small aircraft as a transportation mode in competition with automobile and scheduled commercial air travel by estimating the pool of users that would potentially switch on-demand air travel due to cost/time saving. These new aircraft greatly increase the practicality of regional aircraft as a transportation mode that can avoid the co...

OBJECTIVE The objective of this study was to evaluate the feasibility of using multishot PROPELLER for diffusion-weighted imaging (DWI) of the abdomen. MATERIALS AND METHODS Diffusion-weighted abdominal imaging was performed in 9 healthy volunteers and 3 patients using both single-shot DW-SE-EPI and multishot DW-PROPELLER (BLADE sequence). We compared ADC measurements in phantoms, liver and p...