Topic

# Doppler effect

About: Doppler effect is a research topic. Over the lifetime, 19833 publications have been published within this topic receiving 283429 citations. The topic is also known as: Doppler's principle.

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Mayo Clinic

^{1}TL;DR: The combination of tissue Doppler imaging of the mitral annulus and mitral inflow velocity curves provides better estimates of LV filling pressures than other methods (pulmonary vein, preload reduction), however, accurate prediction of filling pressures for an individual patient requires a stepwise approach incorporating all available data.

Abstract: Background—Noninvasive assessment of diastolic filling by Doppler echocardiography provides important information about left ventricular (LV) status in selected subsets of patients. This study was designed to assess whether mitral annular velocities as assessed by tissue Doppler imaging are associated with invasive measures of diastolic LV performance and whether additional information is gained over traditional Doppler variables. Methods and Results—One hundred consecutive patients referred for cardiac catheterization underwent simultaneous Doppler interrogation. Invasive measurements of LV pressures were obtained with micromanometer-tipped catheters, and the mean LV diastolic pressure (M-LVDP) was used as a surrogate for mean left atrial pressure. Doppler signals from the mitral inflow, pulmonary venous inflow, and TDI of the mitral annulus were obtained. Isolated parameters of transmitral flow correlated with M-LVDP only when ejection fraction <50%. The ratio of mitral velocity to early diastolic veloc...

2,779 citations

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TL;DR: A new method for detecting spikes in acoustic Doppler velocimeter data sequences is suggested and it is shown to have superior performance to various other methods and it has the added advantage that it requires no parameters.

Abstract: A new method for detecting spikes in acoustic Doppler velocimeter data sequences is suggested. The method combines three concepts: (1) that differentiation enhances the high frequency portion of a signal, (2) that the expected maximum of a random series is given by the Universal threshold, and (3) that good data cluster in a dense cloud in phase space or Poincare maps. These concepts are used to construct an ellipsoid in three-dimensional phase space, then points lying outside the ellipsoid are designated as spikes. The new method is shown to have superior performance to various other methods and it has the added advantage that it requires no parameters. Several methods for replacing sequences of spurious data are presented. A polynomial fitted to good data on either side of the spike event, then interpolated across the event, is preferred by the authors.

1,433 citations

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TL;DR: In this paper, the micro-Doppler effect was introduced in radar data, and a model of Doppler modulations was developed to derive formulas of micro-doppler induced by targets with vibration, rotation, tumbling and coning motions.

Abstract: When, in addition to the constant Doppler frequency shift induced by the bulk motion of a radar target, the target or any structure on the target undergoes micro-motion dynamics, such as mechanical vibrations or rotations, the micro-motion dynamics induce Doppler modulations on the returned signal, referred to as the micro-Doppler effect. We introduce the micro-Doppler phenomenon in radar, develop a model of Doppler modulations, derive formulas of micro-Doppler induced by targets with vibration, rotation, tumbling and coning motions, and verify them by simulation studies, analyze time-varying micro-Doppler features using high-resolution time-frequency transforms, and demonstrate the micro-Doppler effect observed in real radar data.

1,373 citations

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TL;DR: In this article, the Doppler effect results from the recoil momentum changing the translational energy of the radiating atom, and it is shown that the assumption that recoil momentum is given to the radii is incorrect if collisions are taking place.

Abstract: Quantum mechanically the Doppler effect results from the recoil momentum changing the translational energy of the radiating atom. The assumption that the recoil momentum is given to the radiating atom is shown to be incorrect if collisions are taking place. If the collisions do not cause broadening by affecting the internal state of the radiator, they result in a substantial narrowing of the Doppler broadened line.

1,243 citations

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TL;DR: In this article, the authors used a fast echelle spectrograph at resolution of R=62,000 and a large format CCD which acquires the entire visible and near IR spectrum in each exposure.

Abstract: Current spectroscopic techniques yield Doppler-shift errors of 10 to 50 m s-1, barely adequate to detect reflex velocities caused by Jupiter-like and lower-mass planets We describe a technique which yields relative radial velocity errors of 3 m s-1 This technique makes use of a fast echelle spectrograph at resolution of R=62,000 and a large format CCD which acquires the entire visible and near IR spectrum in each exposure Starlight is sent through an iodine absorption cell placed at the spectrometer entrance slit The resulting superimposed iodine lines provide a fiducial wavelength scale against which to measure radial velocity shifts The shapes of iodine lines convey the PSF of the spectrometer to account for changes in spectrometer optics and illumination on all times scales We construct a model of each observed spectrum by multiplying a stellar spectrum with an iodine spectrum and convolving the result with the spectrometer PSF The free parameters of the model include the wavelength scale, spectrometer PSF, and stellar Doppler shift All model parameters are derived anew for each exposure and the synthesis is done on a grid of CCD sub-pixels, using spline functions as interpolation predictors We present Doppler tests of the Sun, Tau Ceti, and 107 Psc, observed with the Lick and Keck echelles All exhibit apparent errors of about 3 m s-1, maintained on time scales of minutes to a year This precision agrees with the theoretically predicted errors that stem primarily from photon statistics

1,146 citations