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Nonequispaced grid sampling in photoacoustics with a nonuniform fast Fourier transform

Julian Schmid, Thomas Glatz, Behrooz Zabihian, Mengyang Liu, Wolfgang Drexler, Otmar Scherzer
2016 Journal of Biomedical Optics  
The computational realization is accomplished by the use of a multi-dimensional non-uniform fast Fourier algorithm, where non-uniform data sampling is performed both in frequency and spatial domain.  ...  To obtain the initial pressure from the collected data on a planar sensor arrangement in photoacoustic tomography, there exists an exact analytic frequency domain reconstruction formula.  ...  (2) and (3) . In this paper, we will make use of discretizations of the source function f, the data function g and their Fourier transformsf andĝ, respectively.  ... 
doi:10.1117/1.jbo.21.1.015005 pmid:26780221 fatcat:cwttn5ncorfnjjkc2iezvuzbum

Advanced Methods for Improving the Efficiency of a Shack Hartmann Wavefront Sensor [chapter]

Akondi Vyas, M. B., B. Raghavendra
2012 Topics in Adaptive Optics  
Fast Fourier Transform (FFT) based reconstructor This is a modal reconstruction process where complex exponentials are used as basis functions and the wavefront can be reconstructed from its local discrete  ...  and using the shift property of the discrete Fourier transform on Eq. 10 gives, S x k,l = Φ k,l exp î 2πk N − 1 S y k,l = Φ k,l exp î 2πl N − 1 (11) where S and Φ represent the Fourier transforms of vectors  ... 
doi:10.5772/29884 fatcat:ecno37fm55bgbpmqxp44jlcqaq

Effect of aggregate shapes on local fields in 3D mesoscale simulations of the concrete creep behavior

Fabien Bernachy-Barbe, Benoît Bary
2019 Finite elements in analysis and design  
In this work, the effects of aggregate shapes on the creep response are studied using numerical simulations on 3D mesoscopic samples.  ...  Results obtained with FE and FFT methods are very close, indicating that while FFT is well adapted, FE remains attractive in this context.  ...  Acknowledgements The authors would like to thank Dietmar Meinel from BAM for the X-CT images, EDF and the support from ANR MACENA project, and the following colleagues for the development and use of their  ... 
doi:10.1016/j.finel.2019.01.001 fatcat:phvqyts5y5bavorjuedp2narp4

Global and Regional Features [chapter]

Scott Krig
2014 Computer Vision Metrics  
Images can be described using coding methods or feature descriptors, and images also can be reconstructed from the encodings or from the feature descriptors.  ...  The scatter plot can be made, pixel by pixel, from two images, where pixel pairs form the Cartesian coordinate for scatter plotting using the pixel intensity of image 1 is used as the x coordinate, and  ... 
doi:10.1007/978-1-4302-5930-5_3 fatcat:wh5qyrhtqrav5ip5z3ck7uiqiu

A comparison of distributed memory algorithms for x-ray wave propagation in inhomogeneous media

Sajid Ali, Ming Du, Mark Adams, Barry Smith, Chris Jacobsen
2020 Optics Express  
Calculations of X-ray wave propagation in large objects are needed for modeling diffractive X-ray optics and for optimization-based approaches to image reconstruction for objects that extend beyond the  ...  We find that the first approach suffers from internode communication delays when the transverse array size becomes large, while the second and third approaches have similar scaling to large array size  ...  We also thank Ed Bueler for providing a preprint of the forthcoming book "PETSc for Partial Differential Equations."  ... 
doi:10.1364/oe.400240 pmid:33114856 pmcid:PMC7679186 fatcat:nkmkzzea7bdplmbunm77fbfiea

Compressed sensing for body MRI

Li Feng, Thomas Benkert, Kai Tobias Block, Daniel K. Sodickson, Ricardo Otazo, Hersh Chandarana
2016 Journal of Magnetic Resonance Imaging  
The advent of compressed sensing marks the prelude to a new era of rapid MRI, where the focus of data acquisition has changed from sampling based on the nominal number of voxels and/or frames to sampling  ...  Compressed sensing aims to reconstruct unaliased images from fewer measurements than that are traditionally required in MRI by exploiting image compressibility or sparsity.  ...  Acknowledgments The authors would like to thank Drs. Shreyas Vasanawala, Tao  ... 
doi:10.1002/jmri.25547 pmid:27981664 pmcid:PMC5352490 fatcat:ulfop3kccrg4tdpqsybotylccy

Frequency-time analysis, low-rank reconstruction and denoising of turbulent flows using SPOD [article]

Akhil Nekkanti, Oliver T. Schmidt
2021 arXiv   pre-print
We demonstrate SPOD-based flow field reconstruction using direct inversion of the SPOD algorithm (frequency-domain approach) and propose an alternative approach based on projection of the time series data  ...  While the SPOD optimally represents the flow in a statistical sense, the time-domain approach seeks an optimal reconstruction of each instantaneous flow field.  ...  Acknowledgements We gratefully acknowledge support from Office of Naval Research grant N00014-20-1-2311. The authors would like to thank the anonymous reviewers for their insightful comments.  ... 
arXiv:2011.03644v2 fatcat:rqwtpqqx7vfhxkns3figbz7iqu

Particle shape characterisation using Fourier descriptor analysis

E. T. Bowman, K. Soga, W. Drummond
2001 Geotechnique  
The tech~que uses complex Fourier shape descriptors and image analysis of SEM photographs of sand grain~ to provide an accurate quantification of particle morphology and texture.  ...  of particle irregularity.  ...  Ablett of the Geotechnical Group for technical advice and assistance, Mr A. Heaver of the Materials Group for help with the electron microscopy and Dr M.D.  ... 
doi:10.1680/geot.2001.51.6.545 fatcat:mpsnul7sljcwvejrwzeaasbr5q

A Fourier-wavelet representation of 2-D shapes: sexual dimorphism in the Japanese cranial base

PETE E. LESTREL, ROBERTO M. CESAR Jr., OSAMU TAKAHASHI, EISAKU KANAZAWA
2004 Anthropological Science  
Given a complex irregularly bounded form in Cartesian coordinate space, we first compute elliptical Fourier functions (EFFs) using a set of closely-spaced pseudo-homologous (x, y) points, starting at basion  ...  We present a new approach called computational shape analysis, which utilizes a Fourierwavelet representation for characterizing shape features of 2-D forms commonly encountered in a wide set of sub-disciplines  ...  The interested reader can obtain the software (EFF23) used in part for the preparation of this paper at a nominal cost from the senior author.  ... 
doi:10.1537/ase.00069 fatcat:6tjxkjgvvnhipi4syp6fjxybom

Kaleidoscope: An Efficient, Learnable Representation For All Structured Linear Maps

Tri Dao, Nimit Sharad Sohoni, Albert Gu, Matthew Eichhorn, Amit Blonder, Megan Leszczynski, Atri Rudra, Christopher Ré
2020 International Conference on Learning Representations  
Modern neural network architectures use structured linear transformations, such as low-rank matrices, sparse matrices, permutations, and the Fourier transform, to improve inference speed and reduce memory  ...  In addition, K-matrices can capture latent structure in models: for a challenging permuted image classification task, a K-matrix based representation of permutations is able to learn the right latent structure  ...  , of DARPA, NIH, ONR, or the U.S.  ... 
dblp:conf/iclr/DaoSGEBLRR20 fatcat:kykmhgkyvjcs5c3lzyuh6znmry

Numerical analysis of the non-uniform sampling problem

Thomas Strohmer
2000 Journal of Computational and Applied Mathematics  
We give an overview of recent developments in the problem of reconstructing a band-limited signal from non-uniform sampling from a numerical analysis view point.  ...  Furthermore a fast multilevel algorithm is presented that can reconstruct signals of unknown bandwidth from noisy non-uniformly spaced samples.  ...  The author was supported by NSF DMS grant 9973373. E-mail address: strohmer@math.ucdavis.edu (T. Strohmer)  ... 
doi:10.1016/s0377-0427(00)00361-7 fatcat:23fa4mhk5zckpe4c4ywouc65am

A Time–Frequency Acoustic Emission-Based Technique to Assess Workpiece Surface Quality in Ceramic Grinding with PZT Transducer

Martin A. Aulestia Viera, Paulo R. Aguiar, Pedro Oliveira Junior, Felipe A. Alexandre, Wenderson N. Lopes, Eduardo C. Bianchi, Rosemar Batista da Silva, Doriana D'addona, Andre Andreoli
2019 Sensors  
The results obtained by the PZT diaphragm were similar to the results obtained using the AE sensor. The time–frequency analysis allowed to identify irregularities throughout the monitored process.  ...  Thus, this work presents an analysis of the feasibility of using the acoustic emission signals obtained through the PZT diaphragm, together with digital signal processing in the time–frequency domain,  ...  Acknowledgments: The authors are grateful to the São Paulo Research Foundation-FAPESP for the financial support. Conflicts of Interest: The authors declare no conflict of interest.  ... 
doi:10.3390/s19183913 pmid:31514319 pmcid:PMC6767319 fatcat:zclxqevudzexnef5vua3omrgvy

Information technology: the Lie groups defining the filter banks of the compact disc

Ernst Binz, Walter Schempp
2002 Journal of Computational and Applied Mathematics  
The phenomenal success of the audio CD on the eager worldwide marketplace has encouraged rapid development of CD technology and spawned entirely new high tech applications for the dimpled disc.  ...  The essence of digital audio lies in its numerical basis.  ...  The intrinsic symmetry of the symplectic Fourier transform allows to accelerate the image reconstruction without severe degredation of the picture.  ... 
doi:10.1016/s0377-0427(01)00552-0 fatcat:cdvhnsbv6ffh7heerk6ylyx4wa

Kaleidoscope: An Efficient, Learnable Representation For All Structured Linear Maps [article]

Tri Dao, Nimit S. Sohoni, Albert Gu, Matthew Eichhorn, Amit Blonder, Megan Leszczynski, Atri Rudra, Christopher Ré
2021 arXiv   pre-print
Modern neural network architectures use structured linear transformations, such as low-rank matrices, sparse matrices, permutations, and the Fourier transform, to improve inference speed and reduce memory  ...  In addition, K-matrices can capture latent structure in models: for a challenging permuted image classification task, a K-matrix based representation of permutations is able to learn the right latent structure  ...  We gratefully acknowledge the support of DARPA under Nos.  ... 
arXiv:2012.14966v2 fatcat:64rh5u7es5ei5cc4wiuw7qqca4

The Use of the Wavelet Transform to Extract Additional Information on Surface Quality from Optical Profilometers [chapter]

Richard L.
2012 Advances in Wavelet Theory and Their Applications in Engineering, Physics and Technology  
Acknowledgements The author would like to thank Professor Thomas H. Hodgson for his invaluable help in learning and applying the JTFA techniques discussed in this chapter.  ...  This work was funded by a United States Department of Agriculture: Wood Utilization Research Center Grant.  ...  Thus the DWT is of the same order of computational efficiency as the FFT (where Nlog 2 N multiplications are required) for typical values of n.  ... 
doi:10.5772/38154 fatcat:aojitsv5gbfd5efgqxcooscfc4
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