scholarly journals Three-dimensional snow images by X-ray microtomography

2001 ◽  
Vol 32 ◽  
pp. 75-81 ◽  
Author(s):  
Cécile Coléou ◽  
Bernard Lesaffre ◽  
Jean-Bruno Brzoska ◽  
Wolfgang Ludwig ◽  
Elodie Boller

AbstractFor the first time, three-dimensional (3-D) high-resolution images of snow were obtained using X-ray absorption tomography. Images with a spatial resolution of 10 μm were taken on four different cylindrical snow samples (9 mm high, 9 mm diameter). About 1000 two-dimensional X-ray absorption images were recorded at angular positions of the object around an axis spanning 180°. An appropriate algorithm was then used for these data to reconstruct a 3-D image. In the case of snow, experimental problems have been solved to prepare the samples and prevent both melting and metamorphism of snow during the experiments. This tomographic method provided 3-D data files from which images of 6003 voxels were extracted Several physical parameters of snow microstructure can be processed from these data. Porosity P and discrete local (3-D) curvature C of the grain/pore interface were computed for the four snow samples. Representative elementary volume (REV, in the sense of porous media) is a relevant index to the significance of the sample size with respect to a given parameter. From each image, the values of P and C are compared for subsamples of different size, as an attempt to assess the REVs for porosity and curvature. Results show that the observed volume of snow is statistically significant to achieve the porosity and the curvature distribution.

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Gen-ichiro Yamamoto ◽  
Atsushi Kyono ◽  
Satoru Okada

AbstractMineral trapping through the precipitation of carbonate minerals is a potential approach to reduce CO2 accumulation in the atmosphere. The temperature dependence of amorphous magnesium carbonate (AMC), a precursor of crystalline magnesium carbonate hydrates, was investigated using synchrotron X-ray scattering experiments with atomic pair distribution function (PDF) and X-ray absorption fine structure analysis. PDF analysis revealed that there were no substantial structural differences among the AMC samples synthesized at 20, 60, and 80 °C. In addition, the medium-range order of all three AMC samples was very similar to that of hydromagnesite. Stirring in aqueous solution at room temperature caused the AMC sample to hydrate immediately and form a three-dimensional hydrogen-bonding network. Consequently, it crystallized with the long-range structural order of nesquehonite. The Mg K-edge X-ray absorption near-edge structure spectrum of AMC prepared at 20 °C was very similar to that of nesquehonite, implying that the electronic structure and coordination geometry of Mg atoms in AMC synthesized at 20 °C are highly similar to those in nesquehonite. Therefore, the short-range order (coordination environment) around the Mg atoms was slightly modified with temperature, but the medium-range order of AMC remained unchanged between 20 and 80 °C.


1975 ◽  
Vol 11 (12) ◽  
pp. 4836-4846 ◽  
Author(s):  
E. A. Stern ◽  
D. E. Sayers ◽  
F. W. Lytle

Wear ◽  
1997 ◽  
Vol 202 (2) ◽  
pp. 172-191 ◽  
Author(s):  
Zhanfeng Yin ◽  
Masoud Kasrai ◽  
Marina Fuller ◽  
G.Michael Bancroft ◽  
Kim Fyfe ◽  
...  

Author(s):  
Anatoly Frenkel

We discuss methods of Extended X-ray Absorption Fine-Structure (EXAFS) analysis that provide three-dimensional structural characterization of metal nanoparticles, both mono- and bi-metallic. For the bimetallic alloys, we use short range order measurements to discriminate between random and non-random inter-particle distributions of atoms. We also discuss the application of EXAFS to heterogeneous nanoparticle systems.


2014 ◽  
Vol 11 (S308) ◽  
pp. 368-371
Author(s):  
Jukka Nevalainen ◽  
L. J. Liivamägi ◽  
E. Tempel ◽  
E. Branchini ◽  
M. Roncarelli ◽  
...  

AbstractWe have developed a new method to approach the missing baryons problem. We assume that the missing baryons reside in a form of Warm Hot Intergalactic Medium, i.e. the WHIM. Our method consists of (a) detecting the coherent large scale structure in the spatial distribution of galaxies that traces the Cosmic Web and that in hydrodynamical simulations is associated to the WHIM, (b) mapping its luminosity into a galaxy luminosity density field, (c) using numerical simulations to relate the luminosity density to the density of the WHIM, (d) applying this relation to real data to trace the WHIM using the observed galaxy luminosities in the Sloan Digital Sky Survey and 2dF redshift surveys. In our application we find evidence for the WHIM along the line of sight to the Sculptor Wall, at redshifts consistent with the recently reported X-ray absorption line detections. Our indirect WHIM detection technique complements the standard method based on the detection of characteristic X-ray absorption lines, showing that the galaxy luminosity density is a reliable signpost for the WHIM. For this reason, our method could be applied to current galaxy surveys to optimise the observational strategies for detecting and studying the WHIM and its properties. Our estimates of the WHIM hydrogen column density NH in Sculptor agree with those obtained via the X-ray analysis. Due to the additional NH estimate, our method has potential for improving the constrains of the physical parameters of the WHIM as derived with X-ray absorption, and thus for improving the understanding of the missing baryons problem.


2019 ◽  
Vol 12 (1) ◽  
pp. 501-522 ◽  
Author(s):  
J. Timoshenko ◽  
Z. Duan ◽  
G. Henkelman ◽  
R.M. Crooks ◽  
A.I. Frenkel

Extended X-ray absorption fine structure (EXAFS) spectroscopy is a premiere method for analysis of the structure and structural transformation of nanoparticles. Extraction of analytical information about the three-dimensional structure and dynamics of metal–metal bonds from EXAFS spectra requires special care due to their markedly non-bulk-like character. In recent decades, significant progress has been made in the first-principles modeling of structure and properties of nanoparticles. In this review, we summarize new approaches for EXAFS data analysis that incorporate particle structure modeling into the process of structural refinement.


2000 ◽  
Vol 14 (29n31) ◽  
pp. 3656-3661 ◽  
Author(s):  
N. L. SAINI ◽  
A. LANZARA ◽  
K. B. GARG ◽  
A. BIANCONI ◽  
T. ITO ◽  
...  

Cu K-edge XANES spectroscopy has been used to study local structure around the Cu-site in three-dimensional oxygen deficient perovkite La 8- x Sr x Cu 8 O 20 system. The combination of E//ab and E//c polarization and high resolution XANES spectra on high quality single crystals has allowed us to distinguish the various features associated with the complex Cu-O networks in the system which have then been compared with those of the La 2- x Sr x CuO 4 system.


1999 ◽  
Vol 121 (2) ◽  
pp. 473-482 ◽  
Author(s):  
L. Bassani ◽  
M. Dadina ◽  
R. Maiolino ◽  
M. Salvati ◽  
G. Risaliti ◽  
...  

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