scholarly journals Simulation of the Effect of Coal Microstructures on the Macroscopic Mechanical Behavior

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Yu Fu ◽  
Zhongliang Feng
Keyword(s):  
Spatial Distribution ◽  
Three Dimensional ◽  
Ct Scanning ◽  
Confining Pressure ◽  
Mineral Matter ◽  
Equivalent Diameter ◽  
Box Dimension ◽  
Distribution Characteristics ◽  
Two Phase ◽  
Mineral Structure

This paper investigates the influence of mineral structure on macromechanical behavior of coal under different loading conditions using X-ray CT scanning experimental and numerical methods. The three-dimensional (3D) reconstruction of coal was conducted to assess the spatial distribution characteristics of the mineral structure by AVIZO software. Based on fractal box dimension (BCD) and equivalent diameter, the mineral structures were quantitatively characterized. The 3D finite element models with three distribution characteristics of minerals were built, and the model was considered as a random heterogeneous two-phase material composed of coal matrix and mineral matter. The results show that the frequency of mineral structures decreases with the increase of equivalent diameter in the coal sample. The BCD of the original mineral structure in coal is greater than 2, but the BCD of each part of the minerals divided based on the screening principle is less than 2. Under uniaxial conditions, the elastic modulus, peak strength, and residual strength of coal are monotonically increasing with the size of the mineral structure. The larger the mineral structure size and the more complex the distribution are, the greater the area of stress concentration and the more uniformity the distribution will be. The failure (plasticity) first occurred at the interface between the matrix and the mineral, and the failure zone is significantly different due to the influence of different mineral structures. Under confining pressure, the presence of mineral structure decreases the brittleness of coal, and the variation of brittleness is related to the size and spatial distribution of mineral structures. The fitting relationship between confining pressure and brittleness index is linear, and the correlation coefficient exceeds 0.95.

scholarly journals Spatial distribution characteristics of phaeozem in Songliao Plain based on RS

2020 ◽  
Vol 194 ◽  
pp. 05016
Author(s):  
XING Yu ◽  
Wang Jie ◽  
Yin Yaqiu ◽  
Zhou Yingjie ◽  
Yao Weiling ◽  
...  
Keyword(s):  
Organic Matter ◽  
Spatial Distribution ◽  
Three Dimensional ◽  
Organic Matter Content ◽  
Relevant Information ◽  
Matter Content ◽  
Distribution Characteristics ◽  
Terrain Rendering ◽  
Spatial Distribution Characteristics ◽  
Songliao Plain

Phaeozem is one kind of scarce resources on the earth. Due to the restrictions of natural factors and the influence of human activities over the years, phaeozem degradation has become increasingly serious. Based on images of the ASTER in 2006 and the ETM+ in 2000 in this paper, the phaeozem organic matter content which is greater than 2 ％ was obtained by using quantitative retrieval. Through the three-dimensional remote sensing image, terrain rendering and relevant information were analyzed. On the basis of the above, the spatial distribution characteristics of phaeozem in Songliao Plain were analyzed using DEM (digital elevation model) data. The results show that the total area of phaeozem in Songliao Plain is about 51360.15 km2, and the phaeozem organic matter content is gradually increasing along with the increasing latitude or longitude, and decreasing along with increasing slope. In addition, the soil organic matter content is lower in southern slopes than that in northern slopes.

Micron-scale phenotyping quantification and three-dimensional microstructure reconstruction of vascular bundles within maize stalks based on micro-CT scanning

2017 ◽  
Vol 44 (1) ◽  
pp. 10 ◽  
Author(s):  
Jianjun Du ◽  
Ying Zhang ◽  
Xinyu Guo ◽  
Liming Ma ◽  
Meng Shao ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Spatial Configuration ◽  
Three Dimensional ◽  
Ct Scanning ◽  
Phenotypic Traits ◽  
Vascular Bundles ◽  
Micro Computed Tomography ◽  
Cross Sectional ◽  
Imaging Device ◽  
Maize Stalks

Vascular bundles within maize (Zea mays L.) stalks play a key role in the mechanical support of plant architecture as well as in water and nutrient transportation. Convenient and accurate phenotyping of vascular bundles may help phenotypic identification of germplasm resources for breeding. Based on practical sample preparation procedures for maize stalks, we acquired serials of cross-sectional images using a micro-computed tomography (CT) imaging device. An image processing pipeline dedicated to the phenotyping of vascular bundles was also developed to automatically segment and validate vascular bundles from the cross-sectional images of maize stalks, from which phenotypic traits of vascular bundles, i.e. number, area, and spatial distribution, were calculated. More profound quantification of spatial distribution was given as area ratio of vascular bundles, which described the distribution of vascular bundles associated with the centroid of maize stalks. In addition, three-dimensional visualisation was performed to reveal the spatial configuration and distribution of vascular bundles. The proposed method significantly improves computation accuracy for the phenotypic traits of vascular bundles compared with previous methods, and is expected to be useful for illustrating relationships between phenotypic traits of vascular bundles and their function.

Spatial Distribution of Dialysate in Patients and its Implications to Intradialysate Diffusion

2002 ◽  
Vol 22 (6) ◽  
pp. 698-704 ◽  
Author(s):  
Brian A. Hills ◽  
Seamus Birch ◽  
John R. Burke ◽  
Anthony C. LaMont
Keyword(s):  
Spatial Distribution ◽  
Peritoneal Dialysis ◽  
Spatial Information ◽  
Three Dimensional ◽  
Bulk Diffusion ◽  
Ct Scanning ◽  
Effective Area ◽  
Pelvic Cavity ◽  
Ct Scanner ◽  
Computed Tomographic

Objective To visualize and quantify the spatial distribution of dialysate in patients on continuous ambulatory peritoneal dialysis (CAPD) and, hence, estimate diffusion times for fluid “pockets” wherever intradialysate concentration gradients may not be dissipated by convective currents. Design Contrast medium was added to the dialysate of three supine CAPD patients before an exchange prior to computed tomographic (CT) scanning. Spatial information in the CT scanner was then downloaded to other computers and processed to produce impressive three-dimensional models of dialysate distribution using “wire frame technology.” Results Models differed between patients but all demonstrated pooling of dialysate in the paracolic gutters, subphrenic space, and, especially, in the pelvic cavity. Some pockets of fluid were almost isolated. Quantitatively, the models can account for over 80% of the volume of the exchange (2.5 L), displaying an effective area of contact of 913 – 1450 cm2 between parietal peritoneum and dialysate. This amounts to only 11% – 21% of the anatomic area, again emphasizing the uneven distribution of dialysate. Ignoring very thin (< 0.1 mm) films of dialysate, the bulk (80%) had mean thicknesses ranging from 1.6 to 1.9 cm. Transcendental equations for bulk diffusion were then applied to these findings to determine a theoretical time for urea of about 2 – 3 hours to half-saturation, or 5 – 7 hours to 80% saturation, in the absence of convective currents. Conclusions The distribution of dialysate within the peritoneal cavity is very uneven, resulting in long diffusion times in fluid pockets wherever convective currents may be minimal. Hence, intradialysate diffusion should not be ignored when modeling peritoneal dialysis.

Use of Three-dimensional Printing in the Development of Optimal Cardiac CT Scanning Protocols

2020 ◽  
Vol 16 (8) ◽  
pp. 967-977
Author(s):  
Zhonghua Sun
Keyword(s):  
Cardiovascular Disease ◽  
Cardiac Computed Tomography ◽  
Three Dimensional ◽  
Ct Scanning ◽  
Aortic Diseases ◽  
Clinical Value ◽  
Three Dimensional Printing ◽  
Doctor Patient Communication ◽  
Medical Education And Training ◽  
3D Printed

Three-dimensional (3D) printing is increasingly used in medical applications with most of the studies focusing on its applications in medical education and training, pre-surgical planning and simulation, and doctor-patient communication. An emerging area of utilising 3D printed models lies in the development of cardiac computed tomography (CT) protocols for visualisation and detection of cardiovascular disease. Specifically, 3D printed heart and cardiovascular models have shown potential value in the evaluation of coronary plaques and coronary stents, aortic diseases and detection of pulmonary embolism. This review article provides an overview of the clinical value of 3D printed models in these areas with regard to the development of optimal CT scanning protocols for both diagnostic evaluation of cardiovascular disease and reduction of radiation dose. The expected outcomes are to encourage further research towards this direction.

Simulation of mechanically stirred two-phase liquid-gas flow

1986 ◽  
Vol 51 (5) ◽  
pp. 1001-1015 ◽  
Author(s):  
Ivan Fořt ◽  
Vladimír Rogalewicz ◽  
Miroslav Richter
Keyword(s):  
Spatial Distribution ◽  
Velocity Field ◽  
Gas Flow ◽  
Liquid Velocity ◽  
Model Parameters ◽  
Two Phase ◽  
Mean Velocity ◽  
Rushton Turbine ◽  
Low Viscosity ◽  
Volumetric Gas Flow Rate

The study describes simulation of the motion of bubbles in gas, dispersed by a mechanical impeller in a turbulent low-viscosity liquid flow. The model employs the Monte Carlo method and it is based both on the knowledge of the mean velocity field of mixed liquid (mean motion) and of the spatial distribution of turbulence intensity ( fluctuating motion) in the investigated system - a cylindrical tank with radial baffles at the wall and with a standard (Rushton) turbine impeller in the vessel axis. Motion of the liquid is then superimposed with that of the bubbles in a still environment (ascending motion). The computation of the simulation includes determination of the spatial distribution of the gas holds-up (volumetric concentrations) in the agitated charge as well as of the total gas hold-up system depending on the impeller size and its frequency of revolutions, on the volumetric gas flow rate and the physical properties of gas and liquid. As model parameters, both liquid velocity field and normal gas bubbles distribution characteristics are considered, assuming that the bubbles in the system do not coalesce.

scholarly journals A Microcomputed Tomographic Evaluation of Root Canal Morphology of Maxillary Second Premolars in a Pakistani Cohort

2021 ◽  
Vol 11 (11) ◽  
pp. 5086
Author(s):  
Mazen F. Alkahtany ◽  
Saqib Ali ◽  
Abdul Khabeer ◽  
Shafqat A. Shah ◽  
Khalid H. Almadi ◽  
...  
Keyword(s):  
Root Canal ◽  
Three Dimensional ◽  
Ct Scanning ◽  
Micro Ct ◽  
Single Root ◽  
Root Canal Morphology ◽  
Spss Software ◽  
Variable Morphology ◽  
Canal Morphology

This study aimed to investigate variations in the root canal morphology of maxillary second premolar (MSP) teeth using microcomputed tomography (micro-CT). Sixty (N = 60) human extracted MSPs were collected and prepared for micro-CT scanning. The duration for scanning a single sample ranged between 30 and 40 min and a three-dimensional (3-D) image was obtained for all the MSPs. The images were evaluated by a single observer who recorded the canal morphology type, number of roots, canal orifices, apical foramina(s), apical delta(s), and accessory canals. The root canal configuration was categorized in agreement with Vertucci’s classification, and any configuration not in agreement with Vertucci’s classification was reported as an “additional canal configuration”. Descriptive statistics (such as mean percentages) were calculated using SPSS software. The most common types agreeing with Vertucci’s classification (in order of highest to lowest incidence) were types I, III, V, VII, II, and VI. The teeth also exhibited four additional configurations that were different from Vertucci’s classification: types 2-3, 1-2-3, 2-1-2-1, and 1-2-1-3. A single root was found in 96.7% and the majority of the samples demonstrated two canals (73.3%). Further, 80% of the teeth showed one canal orifice. The number of apical foramina’s in the teeth was variable, with 56.7% having solitary apical foramen. The accessory canal was found in 33.3%, and apical delta was found in only 20% of the samples. Variable morphology of the MSPs was detected in our study. The canal configuration most prevalent was type 1; however, the results also revealed some additional canal types.

Sign in / Sign up

Export Citation Format

Share Document