Results 261 to 270 of about 338,499 (317)

MR Velocity Imaging by Phase Display

Journal of Computer Assisted Tomography, 1985
The ability of the nuclear magnetic resonance signal to encode information about macroscopic motion has been recognized since the works of Hahn and Carr and Purcell. In the medical imaging setting this ability has led to a variety of ingenious magnetic resonance flow imaging schemes that ultimately may become competitive with X-ray angiography in ...
V J, Wedeen, B R, Rosen, D, Chesler, T J, Brady   +3 more
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Nonlinear waves with negative phase velocity

Physical Review E, 2009
Recently, waves propagating with negative phase velocity [simply called antiwaves (AWs)] have attracted great attention in the area of nonlinear oscillatory systems. In the present work we investigate the parameter conditions for AWs. So far AWs have been revealed from systems slightly beyond Hopf bifurcation or some other instabilities, and from some ...
Xiaoqing, Huang, Xuhong, Liao, Xiaohua, Cui, Hong, Zhang, Gang, Hu   +4 more
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Optical refraction in silver: counterposition, negative phase velocity and orthogonal phase velocity

European Journal of Physics, 2011
Complex behaviour associated with metamaterials can arise even in commonplace isotropic dielectric materials. We demonstrate how silver, for example, can support negative phase velocity and counterposition, but not negative refraction, at optical frequencies.
Qaisar A Naqvi, Tom G Mackay, Akhlesh Lakhtakia   +2 more
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Superprism effect based on phase velocities

Optics Letters, 2004
The superprism effect has been studied in the past by use of the anomalous group velocities of optical waves in photonic crystals. We suggest the possibility of realizing agile beam steering based on purely phase-velocity effects. We present designs of photonic crystal prisms that might make experimental observation of this effect possible.
Chiyan, Luo, Marin, Soljacić, J D, Joannopoulos   +2 more
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Gait phase varies over velocities

Gait & Posture, 2014
We sought to characterize the percent (PT) of the phases of a gait cycle (GC) as velocity changes to establish norms for pathological gait characteristics with higher resolution technology. Ninety five healthy subjects (49 males and 46 females with age 34.9 ± 11.8 yrs, body weight 64.0 ± 11.7 kg and BMI 23.5 ± 3.6) were enrolled and walked comfortably ...
Yancheng, Liu, Kun, Lu, Songhua, Yan, Ming, Sun, D Kevin, Lester, Kuan, Zhang   +5 more
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A formula on phase velocity of waves and application

Applied Physics Letters, 2006
Phase velocity plays a key role in wave-matter interactions where phase matching is essential. Laser acceleration of electrons is a good example. We have derived an exact formula with two deductions of the phase velocity for a monochromatic wave field in homogeneous medium from the fundamental wave equation. The core of these formulae is that the phase
Chen, Z., Ho, Y. K., Wang, P. X., Kong, Q., Xie, Y. J., Wang, W., Xu, J. J.   +6 more
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Formula for the phase velocity of electromagnetic waves

Physical Review E, 2009
A new formula for the phase velocity of electromagnetic waves presented by Chen [Appl. Phys. Lett. 88, 121125 (2006)] is investigated and discussed here. The difference between the result obtained with the new formula and that obtained directly using the phase term is small for a fundament-mode Gaussian laser beam.
Shihua, Huang, Fengmin, Wu, Bo, Hu
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On the phase velocity and group velocity of guided waves

Journal of Mathematical Physics, 1973
Relations between the phase velocity and group velocity of guided waves in homogeneous media and the restrictions under which they can be generalized to inhomogeneous media are discussed. Dirichlet, Neumann, and mixed boundary conditions are considered, including the case of frequency dependent media and boundary conditions.
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Second-harmonic generation under phase-velocity and group-velocity mismatch: influence of cascading self-phase and cross-phase modulation

Optics Letters, 1997
Temporal and spectral characteristics of pulses resulting from second-harmonic generation of 120-fs amplified Ti:sapphire laser pulses up to 0.1 mJ at a wavelength of 815 nm in type I KDP crystal were experimentally and theoretically analyzed. Widely different behaviors were observed, according to the sign of the phase mismatch.
Rassoul, R. M., Ivanov, A., Freysz, E., Ducasse, A., Hache, F.   +4 more
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Phase Velocity in Resonant Structures

INTERMAG 2006 - IEEE International Magnetics Conference, 2006
We present a simple experimental procedure for testing of the phase-velocity behavior with respect to the effective material properties as demonstrated by the field dependent behavior of the metafilm. We have demonstrated that the phase-velocity behavior of an effective parameter material under different conditions, and have shown that a negative-phase
J. Baker-Jarvis, M.D. Janezic, D. Love, T.M. Wallis, C.L. Holloway, P. Kabos   +5 more
openaire   +1 more source