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Traditionally, measuring the center-of-mass (c.m.) velocity of an atomic ensemble relies on measuring the Doppler shift of the absorption spectrum of single atoms in the ensemble. Mapping out the velocity distribution of the ensemble is…

Atomic Physics · Physics 2020-03-10 Zilong Chen , Hong Ming Lim , Chang Huang , Rainer Dumke , Shau-Yu Lan

Doppler tomography is a method to compute the emissivity distribution within the co-rotating frames of binary stars from observations of their emission line profiles at multiple orbital phases. A key assumption of the method as it is…

Solar and Stellar Astrophysics · Physics 2021-12-08 T. R. Marsh

Doppler tomography is a technique that has revolutionised the interpretation of the phase-resolved spectroscopic observations of interacting binary systems. We present the results of our investigation of reversing the velocity axis to…

Solar and Stellar Astrophysics · Physics 2015-07-21 E. J. Kotze , S. B. Potter , V. A. McBride

Spectral Doppler ultrasound imaging allows visualizing blood flow by estimating its velocity distribution over time. Duplex ultrasound is a modality in which an ultrasound system is used for displaying simultaneously both B-mode images and…

Information Theory · Computer Science 2018-08-03 Regev Cohen , Yonina C. Eldar

Absorption imaging and spectroscopy can probe the dynamics of an ultracold neutral plasma during the first few microseconds after its creation. Quantitative analysis of the data, however, is complicated by the inhomogeneous density…

In comparison to numerous enhanced sampling methods for equilbrium thermodynamics, accelerating simulations for kinetics and nonequilibrium statistics are relatively rare and less effective. Here we derive a time-reversal path sampling…

Chemical Physics · Physics 2023-11-10 Zhirong Liu

A velocity-map-imaging spectrometer is demonstrated to characterize the normalized transverse emittance of photoemitted electron bunches. The two-dimensional (2D) projected velocity distribution images of photoemitted electrons are recorded…

We develop a sampling scheme on the sphere that permits accurate computation of the spherical harmonic transform and its inverse for signals band-limited at $L$ using only $L^2$ samples. We obtain the optimal number of samples given by the…

Information Theory · Computer Science 2014-07-25 Zubair Khalid , Rodney A. Kennedy , Jason D. McEwen

We present measurements of the velocity distribution of calcium atoms in an atomic beam generated using a dual-stage laser back-ablation apparatus. Distributions are measured using a velocity selective Doppler time-of-flight technique. They…

Atomic Physics · Physics 2008-10-29 A. Denning , A. Booth , S. Lee , M. Ammonson , S. D. Bergeson

I review the method of Doppler tomography which translates binary-star line profiles taken at a series of orbital phases into a distribution of emission over the binary. I begin with a discussion of the basic principles behind Doppler…

Astrophysics · Physics 2007-05-23 T. R. Marsh

Diffusion-based samplers learn to sample complex, high-dimensional distributions using energies or log densities alone, without training data. Yet, they remain impractical for molecular sampling because they are often slower than molecular…

We consider the inverse problem of determining the geometry of penetrable objects from scattering data generated by one incident wave at a fixed frequency. We first study an orthogonality sampling type method which is fast, simple to…

Numerical Analysis · Mathematics 2022-07-21 Thu Le , Dinh-Liem Nguyen , Vu Nguyen , Trung Truong

For many applications, such as computing the expected value of different magnitudes, sampling from a known probability density function, the target density, is crucial but challenging through the inverse transform. In these cases, rejection…

Machine Learning · Computer Science 2020-03-24 Sebastian Pina-Otey , Thorsten Lux , Federico Sánchez , Vicens Gaitan

Diffusion probabilistic models (DPMs) have been shown to generate high-quality images without the need for delicate adversarial training. However, the current sampling process in DPMs is prone to violent shaking. In this paper, we present a…

Computer Vision and Pattern Recognition · Computer Science 2023-08-24 Xiyu Wang , Anh-Dung Dinh , Daochang Liu , Chang Xu

We introduce Doppler time-of-flight (D-ToF) rendering, an extension of ToF rendering for dynamic scenes, with applications in simulating D-ToF cameras. D-ToF cameras use high-frequency modulation of illumination and exposure, and measure…

Graphics · Computer Science 2023-10-06 Juhyeon Kim , Wojciech Jarosz , Ioannis Gkioulekas , Adithya Pediredla

Umbrella sampling is an efficient method for the calculation of free energy changes of a system along well-defined reaction coordinates. However, when multiple parallel channels along the reaction coordinate or hidden barriers in directions…

Methodology · Statistics 2015-06-16 Mingjun Yang , Lijiang Yang , Yiqin Gao , Hao Hu

Just as the ordinary Doppler effect serves as a tool to measure radial velocities of celestial objects, so can the relativistic Doppler effect be implemented to measure a combination of radial and transverse velocities by using recent…

Astrophysics · Physics 2016-01-13 Leonid M. Ozernoy

Sampling from high-dimensional distributions is a fundamental problem in statistical research and practice. However, great challenges emerge when the target density function is unnormalized and contains isolated modes. We tackle this…

Methodology · Statistics 2023-04-11 Yixuan Qiu , Xiao Wang

We propose a novel direct sampling method (DSM) for the effective and stable inversion of the Radon transform. The DSM is based on a generalization of the important almost orthogonality property in classical DSMs to fractional order Sobolev…

Numerical Analysis · Mathematics 2020-10-22 Yat Tin Chow , Fuqun Han , Jun Zou

The measurement of Doppler velocity shifts in spectra is a ubiquitous theme in astronomy, usually handled by computing the cross-correlation of the signals, and finding the location of its maximum. This paper addresses the problem of the…

Astrophysics · Physics 2008-11-26 Carlos Allende Prieto
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