We analyzed the standing balance control of 11 healthy subjects and 15 subjects with bilateral vestibular hypofunction (BVH) using phase plane (velocity versus displacement) plots. We hypothesized that maintaining postural stability requires control of both the position and momentum of the center of gravity (CG) and infer that it is advantageous to use both velocity and displacement data to cha...

TWTs for space applications commonly have a helix pitch profile which incorporates a section with increased phase velocity followed by a negative phase velocity taper. A simple method is described for the initial design of a helix slow-wave structure of this kind to achieve high overall efficiency. It is shown that the use of a section with increased phase velocity increases the beam efficiency...

The planewave response of bianisotropic materials generally cannot be characterized by a single scalar index, as directionality of energy flow and multiple wavevectors need to be considered. This is especially significant for bianisotropic metamaterials which support negative refraction, negative phase velocity, and counterposition. By means of a numerical example based on a commonly–studied bi...

The term "artificial dielectric" is conveniently applied to any arrangement of conducting obstacles which affects the propagation of electromagnetic waves in a way similar to a solid dielectric. The essential property of a solid dielectric from the point of view of propagation is that the phase velocity within the dielectric is different from the free-space value. A quantitative indication of t...

Objectives • To review recent advances in phase contrast MRI methodology that allow for 4D Flow MRI acquisitions in clinically feasible scan times. • To review physiological markers that can be obtained with 4D Flow MRI, including vorticity, pressure maps, pulse wave velocity, .and wall shear stress. • To review potential limitations and potential sources of errors for velocity mapping and para...

BACKGROUND Time-resolved three-dimensional, three-directional phase-contrast magnetic resonance velocity mapping (4D PC-MRI) is a powerful technique to depict dynamic blood flow patterns in the human body. However, the impact of phase background effects on flow visualizations has not been thoroughly studied previously, and it has not yet been experimentally demonstrated to what degree phase off...

conclusions according to the findings of the current study, both open-loop and closed-loop neuromuscular control mechanisms altered in patients with cai. methods it was a case-control study. twenty-two subjects with unilateral cai and 22 healthy subjects stood on a force plate and initiated gait with maximal velocity under 2 conditions: i) planned (initiated gait after hearing the “all set” sig...

Geometric dispersion is commonly observed in shallow water marine data due to post-critical multiples in the water layer over a hard seafloor. Characteristics of the guided waves include formation of distinct propagation modes and associated divergence of phase and group velocity. Methods have been available since 1981 to image phase velocity dispersion curves. Here we report a method to direct...

We present a phase retrieval method (PRM) for analyzing single-phase displacement interferometry measurements on rapidly changing velocity histories, including photon Doppler velocimetry (PDV). PRM identifies the peaks and valleys as well as zero-crossing points in a PDV time series, performs normalization and extracts point-by-point phase and thus velocity information. PRM does not require a w...

A thin, annular plasma sheet in a waveguide slows down the phase velocity of electromagnetic modes in a plasma density window for frequencies below the electron cyclotron frequency via cerenkov interaction. At lower densities, the plasma is not effective enough to reduce the phase velocity of the em waves below c. At higher densities the plasma expels the radiation field leading to enhancement ...