scholarly journals Selection of material for X-ray tomography analysis and DEM simulations: comparison between granular materials of biological and non-biological origins

2018 ◽  
Vol 20 (3) ◽  
Author(s):  
L. Babout ◽  
K. Grudzień ◽  
J. Wiącek ◽  
M. Niedostatkiewicz ◽  
B. Karpiński ◽  
...  
Keyword(s):  
Granular Materials ◽  
X Ray ◽  
Dem Simulations ◽  
Tomography Analysis ◽  
Selection Of

X‐ray tomography analysis of soil biopores structure under wetting and drying cycles

2021 ◽  
Author(s):  
Sougueh Cheik ◽  
Pascal Jouquet ◽  
Jean‐Luc Maeght ◽  
Yvan Capowiez ◽  
T.M. Tran ◽  
...  
Keyword(s):  
Wetting And Drying ◽  
X Ray ◽  
Wetting And Drying Cycles ◽  
Tomography Analysis

scholarly journals Penetration strength of coarse granular materials from DEM simulations

2013 ◽  
Author(s):  
Juan Carlos Quezada ◽  
Gilles Saussine ◽  
Pierre Breul ◽  
Farhang Radjai
Keyword(s):  
Granular Materials ◽  
Dem Simulations

scholarly journals EM Estimation of the X-Ray Spectrum With a Genetically Optimized Step-Wedge Phantom

2021 ◽  
Vol 9 ◽  
Author(s):  
Mengzhou Li ◽  
Feng-Lei Fan ◽  
Wenxiang Cong ◽  
Ge Wang
Keyword(s):  
Energy Spectrum ◽  
Condition Number ◽  
Linear Equations ◽  
Spectrum Estimation ◽  
Genetic Optimization ◽  
System Matrix ◽  
X Ray ◽  
Phantom Design ◽  
Selection Of ◽  
Spectrum Inversion

The energy spectrum of an X-ray tube plays an important role in computed tomography (CT), and is often estimated from physical measurement of dedicated phantoms. Usually, this estimation problem is reduced to solving a system of linear equations, which is generally ill-conditioned. In this paper, we optimize a phantom design to find the most effective combinations of thicknesses for different materials. First, we analyze the ill-posedness of the energy spectrum inversion when the number of unknown variables (N) and measurements (M) are equal, and show the condition number of the system matrix increases exponentially with N if the transmission thicknesses are linearly changed. Then, we present a genetic optimization algorithm to minimize the condition number of the system matrix in a general case (M < N) with respect to the selection of thicknesses and types of phantom materials. Finally, in the simulation with Poisson noise we study the accuracy of the spectrum estimation using the expectation-maximum algorithm. Our results indicate that the proposed method allows high-quality spectrum estimation, and the number of measurements is reduced over two thirds of that required by the widely-used method using a phantom with linearly-changed thicknesses.

Interactive selection of JPEG quantization tables for digital x-ray image compression

1993 ◽  
Author(s):  
Lewis E. Berman ◽  
Babak Nouri ◽  
Gautam Roy ◽  
Leif Neve
Keyword(s):  
Image Compression ◽  
X Ray ◽  
Interactive Selection ◽  
Selection Of

Selection of target elements for laser-produced plasma soft x-ray sources

2018 ◽  
Vol 43 (9) ◽  
pp. 2042 ◽  
Author(s):  
Toshiki Tamura ◽  
Goki Arai ◽  
Yoshiki Kondo ◽  
Hiroyuki Hara ◽  
Tadashi Hatano ◽  
...  
Keyword(s):  
X Ray ◽  
Laser Produced Plasma ◽  
Selection Of

Recollimation shocks in relativistic jets

2018 ◽  
Vol 27 (10) ◽  
pp. 1844011 ◽  
Author(s):  
José M. Martí ◽  
Manel Perucho ◽  
José L. Gómez ◽  
Antonio Fuentes
Keyword(s):  
Magnetic Fields ◽  
Numerical Simulations ◽  
Theoretical Background ◽  
Synchrotron Emission ◽  
Relativistic Jets ◽  
Dominant Type ◽  
X Ray ◽  
Extragalactic Jets ◽  
X Ray Binaries ◽  
Selection Of

Recollimation shocks (RS) appear associated with relativistic flows propagating through pressure mismatched atmospheres. Astrophysical scenarios invoking the presence of such shocks include jets from AGNs and X-ray binaries and GRBs. We shall start reviewing the theoretical background behind the structure of RS in overpressured jets. Next, basing on numerical simulations, we will focus on the properties of RS in relativistic steady jets threaded by helical magnetic fields depending on the dominant type of energy. Synthetic radio maps from the simulation of the synchrotron emission for a selection of models in the context of parsec-scale extragalactic jets will also be discussed.

scholarly journals Solidified Fillings of Nanopores

2005 ◽  
Vol 876 ◽  
Author(s):  
Patrick Huber ◽  
Klaus Knorr
Keyword(s):  
Pore Diameter ◽  
Stacking Faults ◽  
Pore Geometry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Medium Length ◽  
Close Packed Structure ◽  
Packed Structure ◽  
Diffraction Patterns ◽  
Selection Of

AbstractWe present a selection of x-ray diffraction patterns of spherical (He, Ar), dumbbell- (N2, CO), and chain-like molecules (n-C9H20, n-C19H40) solidified in nanopores of silica glass (mean pore diameter 7nm). These patterns allow us to demonstrate how key principles governing crystallization have to be adapted in order to accomplish solidification in restricted geometries. 4He, Ar, and the spherical close packed phases of CO and N2 adjust to the pore geometry by introducing a sizeable amount of stacking faults. For the pore solidified, medium-length chainlike n-C19H40 we observe a close packed structure without lamellar ordering, whereas for the short-chain C9H20 the layering principle survives, albeit in a modified fashion compared to the bulk phase.

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