Contaminant migration in unsaturated porous media using X-ray computerized tomography (CT)

2013 ◽  
Vol 69 (5) ◽  
pp. 953-959 ◽  
Author(s):  
Nian Qing Zhou ◽  
Shan Zhao ◽  
Wei Song ◽  
Jun Otani
Keyword(s):  
Porous Media ◽  
Computerized Tomography ◽  
Three Dimensional ◽  
Ct Scanning ◽  
Silica Sand ◽  
Unsaturated Porous Media ◽  
Contaminant Migration ◽  
X Ray ◽  
Before And After ◽  
Unsaturated Zones

Landfills are usually located in unsaturated zones. Contaminant leaking can easily infiltrate groundwater through these porous media and contribute to groundwater pollution. The main objective of this work is to study the leachate migration in unsaturated porous media using X-ray computerized tomography (CT) and image-processing software. Silica sand and Yamazuna sand (collected from Japan) with different particle sizes are considered. Potassium iodide (KI) solution is used as a contaminant and injected into sand specimens at appropriate rates. The specimens are scanned at each cross section before and after contaminant injection by X-ray CT. Subsequently, all CT images are transformed into mean CT values by Image J software. VGStudio software is then used to reconstruct the subtracted images into three-dimensional images. The results indicate that vertical migration is dominant in uniform sand and horizontal migration is the main behavior in well-graded sand. Meanwhile, it is also confirmed that CT scanning is an effective technology to study contaminant migration in unsaturated porous media with different grain sizes.

scholarly journals In Situ Coherent X-ray Diffraction during Three-Point Bending of a Au Nanowire: Visualization and Quantification

2018 ◽  
Vol 2 (4) ◽  
pp. 24 ◽  
Author(s):  
Anton Davydok ◽  
Thomas Cornelius ◽  
Zhe Ren ◽  
Cedric Leclere ◽  
Gilbert Chahine ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Reciprocal Space ◽  
X Ray Diffraction ◽  
Complex Deformation ◽  
X Ray ◽  
Three Point Bending ◽  
Atomic Force ◽  
Au Nanowire ◽  
Before And After

The three-point bending behavior of a single Au nanowire deformed by an atomic force microscope was monitored by coherent X-ray diffraction using a sub-micrometer sized hard X-ray beam. Three-dimensional reciprocal-space maps were recorded before and after deformation by standard rocking curves and were measured by scanning the energy of the incident X-ray beam during deformation at different loading stages. The mechanical behavior of the nanowire was visualized in reciprocal space and a complex deformation mechanism is described. In addition to the expected bending of the nanowire, torsion was detected. Bending and torsion angles were quantified from the high-resolution diffraction data.

Measurement Method of X-ray Focus Projection Coordinates of Three-Dimensional Micro-Computerized Tomography Scanning System

2009 ◽  
Vol 29 (5) ◽  
pp. 1275-1280
Author(s):  
杨民 Yang Min ◽  
刘静华 Liu Jinghua ◽  
李保磊 Li Baolei ◽  
吴文晋 Wu Wenjin ◽  
王钢 Wang Gang
Keyword(s):  
Computerized Tomography ◽  
Measurement Method ◽  
Three Dimensional ◽  
Scanning System ◽  
X Ray ◽  
Tomography Scanning ◽  
Focus Projection

scholarly journals Reconstruction and Analysis of Tight Sandstone Digital Rock Combined with X-Ray CT Scanning and Multiple-Point Geostatistics Algorithm

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yun Lei
Keyword(s):  
Pore Space ◽  
Full Range ◽  
Three Dimensional ◽  
Ct Scanning ◽  
Multiple Point ◽  
Tight Sandstone ◽  
Sandstone Sample ◽  
X Ray ◽  
Digital Rock ◽  
Experimental Values

Unconventional rocks such as tight sandstone and shale usually develop multiscale complex pore structures, with dimensions ranging from nanometers to millimeters, and the full range can be difficult to characterize for natural samples. In this paper, we developed a new hybrid digital rock construction approach to mimic the pore space of tight sandstone by combining X-ray CT scanning and multiple-point geostatistics algorithm (MPGA). First, a three-dimensional macropore digital rock describing the macroscopic pore structure of tight sandstone was constructed by micro-CT scanning. Then, high-resolution scanning electron microscopy (SEM) was performed on the tight sandstone sample, and the three-dimensional micropore digital rock was reconstructed by MPGA. Finally, the macropore digital rock and the micropore digital rock were superimposed into the full-pore digital rock. In addition, the nuclear magnetic resonance (NMR) response of digital rocks is simulated using a random walk method, and seepage simulation was performed by the lattice Boltzmann method (LBM). The results show that the full-pore digital rock has the same anisotropy and good connectivity as the actual rock. The porosity, NMR response, and permeability are in good agreement with the experimental values.

Three-dimensional computerized tomography angiography in patients with hyperacute intracerebral hemorrhage

1999 ◽  
Vol 91 (3) ◽  
pp. 424-431 ◽  
Author(s):  
Yasuo Murai ◽  
Ryo Takagi ◽  
Yukio Ikeda ◽  
Yasuhiro Yamamoto ◽  
Akira Teramoto
Keyword(s):  
Intracerebral Hemorrhage ◽  
Ct Angiography ◽  
Computerized Tomography ◽  
Three Dimensional ◽  
Ct Scanning ◽  
3D Ct ◽  
Content Type ◽  
Hematoma Enlargement ◽  
3D Ct Angiography ◽  
Fine Print

Object. The authors confirm the usefulness of extravasation detected on three-dimensional computerized tomography (3D-CT) angiography in the diagnosis of continued hemorrhage and establishment of its cause in patients with acute intracerebral hemorrhage (ICH).Methods. Thirty-one patients with acute ICH in whom noncontrast and 3D-CT angiography had been performed within 12 hours of the onset of hemorrhage and in whom conventional cerebral angiographic studies were obtained during the chronic stage were prospectively studied. Noncontrast CT scanning was repeated within 24 hours of the onset of ICH to evaluate hematoma enlargement.Findings indicating extravasation on 3D-CT angiography, including any abnormal area of high density on helical CT scanning, were observed in five patients; three of these demonstrated hematoma enlargement on follow-up CT studies. Thus, specificity was 60% (three correct predictions among five positives) and sensitivity was 100% (19 correct predictions among 19 negatives). Evidence of extravasation on 3D-CT angiography indicates that there is persistent hemorrhage and correlates with enlargement of the hematoma.Regarding the cause of hemorrhage, five cerebral aneurysms were visualized in four patients, and two diagnoses of moyamoya disease and one of unilateral moyamoya phenomenon were made with the aid of 3D-CT angiography. Emergency surgery was performed without conventional angiography in one patient who had an aneurysm, and it was clipped successfully.Conclusions. Overall, 3D-CT angiography was found to be valuable in the diagnosis of the cause of hemorrhage and in the detection of persistent hemorrhage in patients with acute ICH.

Significance of contrast enhancement in cranial computerized tomography after subarachnoid hemorrhage

1984 ◽  
Vol 60 (2) ◽  
pp. 335-342 ◽  
Author(s):  
Thomas Doczi ◽  
James Ambrose ◽  
Sean O'Laoire
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Contrast Enhancement ◽  
Computerized Tomography ◽  
Contrast Material ◽  
Ct Scanning ◽  
Visual Evaluation ◽  
Content Type ◽  
Before And After ◽  
Subarachnoid Spaces ◽  
Cranial Computerized Tomography

✓ Eighty patients with subarachnoid hemorrhage underwent computerized tomography (CT) scanning before and after administration of Conray contrast medium. Abnormal enhancement was seen in visual evaluation of the CT scans in 26 cases, in the regions bordering the subarachnoid spaces. Abnormal enhancement was associated with a poor clinical condition, angiographic spasm, and a poor outcome. Measurements of absorption values in the thalamus revealed significant increases in density after contrast enhancement in those patients whose scans showed abnormal enhancement in the regions bordering the subarachnoid spaces on visual evaluation. The authors suggest that the abnormal enhancement is parenchymal, in the gyri, and is not “subarachnoid.” They suggest that it is due to gyral hyperemia or extravasation of contrast material into the cortex resulting from breakdown of the blood-brain barrier, or a combination of both factors.

Sign in / Sign up

Export Citation Format

Share Document