Results 51 to 60 of about 1,101,667 (305)

Quadratic Fourier Transforms [PDF]

open access: yesAnnals of Functional Analysis, 2014
In this paper we shall examine the quadratic Fourier transform which is introduced by the generalized quadratic function for one order parameter in the ordinary Fourier transform. This will be done by analyzing corresponding six subcases of the quadratic Fourier transform within a reproducing kernel Hilbert spaces framework.
Castro, L. P.   +4 more
openaire   +4 more sources

Fast complexified quaternion Fourier transform

open access: yes, 2006
A discrete complexified quaternion Fourier transform is introduced. This is a generalization of the discrete quaternion Fourier transform to the case where either or both of the signal/image and the transform kernel are complex quaternion-valued.
Bihan Stephen   +3 more
core   +4 more sources

An approach for coherent periodogram averaging of tilt‐series data for improved contrast transfer function estimation

open access: yesFEBS Open Bio, EarlyView.
The contrast transfer function (CTF) is an imaging aberration that is a major resolution‐limiting factor in cryo‐electron microscopy (cryo‐EM). Precise CTF estimation is key to overcoming this limitation, but is particularly challenging in cryo‐electron tomography (cryo‐ET) data. Here, we present an approach for using geometric information to assist in
Sagar Khavnekar, William Wan
wiley   +1 more source

Reviews of bearing vibration measurement using fast Fourier transform and enhanced fast Fourier transform algorithms

open access: yesAdvances in Mechanical Engineering, 2019
The rolling element bearing is one of the most critical components in a machine. Vibration signals resulting from these bearings imply important bearing defect information related to the machinery faults.
Hsiung-Cheng Lin, Yu-Chen Ye
doaj   +1 more source

Mechanochemical Synthesis and Characterization of Nanostructured ErB4 and NdB4 Rare‐Earth Tetraborides

open access: yesAdvanced Engineering Materials, Volume 27, Issue 6, March 2025.
ErB4 and NdB4 nanostructured powders are produced by mechanochemical synthesis. 5 h mechanical alloying and 4 M HCl acid leaching are used in the production. ErB4 and NdB4 powders exhibit maximum magnetization of 0.4726 emu g−1 accompanied with an antiferromagnetic‐to‐paramagnetic phase transition at about TN = 18 K and 0.132 emu g−1 with a maximum at ...
Burçak Boztemur   +5 more
wiley   +1 more source

Fourier transform noise spectroscopy

open access: yesnpj Quantum Information
Spectral characterization of noise environments that lead to the decoherence of qubits is critical to developing robust quantum technologies. While dynamical decoupling offers one of the most successful approaches to characterize noise spectra, it ...
Arian Vezvaee   +3 more
doaj   +1 more source

Phase-controlled Fourier-transform spectroscopy

open access: yesNature Communications, 2018
Fourier transform spectrometers are generally limited to slow scanning rates at high resolution. Here the authors demonstrate highly efficient Fourier transform spectroscopy using a dynamic phase-control technique that enables fast acquisition without ...
Kazuki Hashimoto, Takuro Ideguchi
doaj   +1 more source

Mechanisms of Increasing Weld Depth during Temporal Power Modulation in High‐Power Laser Beam Welding

open access: yesAdvanced Engineering Materials, EarlyView.
Temporal power modulation increases weld depth in high‐power laser beam welding of dissimilar round bars by nearly 20% compared to same average continuously welded welding power. The mechanism of action also applies to sheet welding and depends on the inertia of keyhole depth for the modulated laser beam power.
Jan Grajczak   +7 more
wiley   +1 more source

A hyperkähler Fourier transform

open access: yesDifferential Geometry and its Applications, 1998
AbstractGiven two hyperkähler manifolds X and Y and a quaternionic instanton on X × Y, one can define a Fourier-Mukai transform, which maps quaternionic instantons on X to quaternionic instantons on Y. This construction encompasses the cases of two-dimensional algebraic tori and K3 surfaces already treated elsewhere.
BARTOCCI, CLAUDIO   +2 more
openaire   +3 more sources

Steerable Discrete Fourier Transform

open access: yes, 2017
Directional transforms have recently raised a lot of interest thanks to their numerous applications in signal compression and analysis. In this letter, we introduce a generalization of the discrete Fourier transform, called steerable DFT (SDFT).
Fracastoro, Giulia, Magli, Enrico
core   +1 more source

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