scholarly journals Rock Breaking and Dynamic Response Characteristics of Carbon Dioxide Phase Transition Fracturing Considering the Gathering Energy Effect

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1336 ◽  
Author(s):  
Shengtao Zhou ◽  
Nan Jiang ◽  
Xu He ◽  
Xuedong Luo
Keyword(s):  
Phase Transition ◽  
Carbon Dioxide ◽  
Dynamic Response ◽  
Rock Breaking ◽  
Energy Effect ◽  
Secondary Impact ◽  
Peak Point ◽  
Point Velocity ◽  
The Impact ◽  
Primary Impact

Carbon dioxide phase transition fracturing has been widely used in rock mass excavation under complex environments, and its special rock breaking process shows obvious gathering energy effect. In this paper, the gathering energy effect of this technology is considered and then the impact reduction coefficient is defined and determined. Eventually, a combined method of field tests and numerical simulations is used to study the crack propagation characteristics and spatiotemporal changes of dynamic response. The results show that the cracks grow more and more slowly as time goes by; the peak displacement and peak point velocity in the primary impact direction are both greater than those in the secondary impact direction. The peak point velocity in different directions decreases as the distance from borehole increases and it decays more and more slowly. With the increase of distance from the borehole, the peak effective stress in the primary impact direction constantly decreases. However, it increases first and then decreases in the secondary impact direction. The results mentioned above can provide effective guidance for later experimental research and engineering.

scholarly journals Experimental Study on Explosion Pressure and Rock Breaking Characteristics under Liquid Carbon Dioxide Blasting

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Yanan Zhang ◽  
Junren Deng ◽  
Bo Ke ◽  
Hongwei Deng ◽  
Jielin Li
Keyword(s):  
Carbon Dioxide ◽  
High Pressure ◽  
Free Field ◽  
Jet Impingement ◽  
Rock Breaking ◽  
Tensile Failure ◽  
Liquid Carbon ◽  
Liquid Carbon Dioxide ◽  
Explosion Pressure ◽  
The Impact

A liquid carbon dioxide blasting experiment was carried out under free field conditions, alongside a liquid carbon dioxide rock breaking experiment, to investigate explosion pressure variation and rock breaking characteristics under liquid carbon dioxide blasting. The experimental results show that the internal and external explosion pressures of the liquid carbon dioxide fracturing devices all rapidly increased at first, before attenuating vibrantly after blasting. When the explosion pressure was raised, the internal explosion pressure increased first exponentially and then linearly, while the external explosion pressure increased exponentially throughout. The duration time of the blasting effect stage was about 45 ms. Under the combined effect of jet impingement and a gas wedge of high-pressure carbon dioxide, the rock is subjected to tensile failure. The impact failure and the “gas wedge effect” of high-pressure carbon dioxide play a key role in the rock breaking of liquid carbon dioxide blasting technology.

scholarly journals Experimental Investigation on Influencing Factors of Rock Fragmentation Induced by Carbon Dioxide Phase Transition Fracturing

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Bo Gao ◽  
Youjiang Yang ◽  
Weilong Xue ◽  
Anhui Guo ◽  
Xuedong Luo
Keyword(s):  
Phase Transition ◽  
Carbon Dioxide ◽  
Growth Rate ◽  
Field Experiments ◽  
Sheet Thickness ◽  
Peak Stress ◽  
Rock Breaking ◽  
Rock Fragmentation ◽  
Powder Factor ◽  
Crater Volume

Carbon dioxide phase transition fracturing is a novel physical blasting technique, which is gradually used in mining and underground space engineering. The improvement of its rock breaking efficiency is the key concern in the application. In this paper, field experiments of CO2 phase transition fracturing were conducted. Based on the strain monitoring and fracturing crater volume measuring, the variation of CO2 filling amount and shear sheet thickness on rock fragmentation of CO2 phase transition fracturing was investigated. The experimental results indicated that the fracturing crater is shaped as an elliptical cone that is longer in the jet direction and shorter in the vertical jet direction. With the increase of the CO2 filling amount, the excavated crater volume gradually increases, but the growth rate gradually decreases. The powder factor is constant within a certain charge amount, and after exceeding this charge amount, the powder factor of CO2 increases significantly. As the shear sheet thickness increases, although the consultant peak stress gradually increases, its growth rate is still unchanged. The crater volume and its growth rate gradually increase in the same situation. Moreover, with the shear sheet thickness increase, the CO2 powder factor decreases continuously, and the decline rate remains unchanged.

scholarly journals Meshing Contact Impact Properties of Circular Arc Tooth Trace Cylindrical Gear Based on Rotating Knife Dish Milling Process

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Dengqiu Ma ◽  
Yongping Liu ◽  
Zhenhuan Ye ◽  
Yongqiao Wei ◽  
Dawei Li ◽  
...  
Keyword(s):  
Tooth Surface ◽  
Cylindrical Gear ◽  
Secondary Impact ◽  
Impact Stress ◽  
Impact Position ◽  
Distribution Rule ◽  
Contact Impact ◽  
Set Up ◽  
The Impact ◽  
Primary Impact

Taking the circular arc tooth trace (CATT) cylindrical gear as a research object, in order to obtain the CATT cylindrical gear’s meshing contact impact properties, the meshing contact impact hypothesis of the CATT cylindrical gear was put forward based on the contact dynamics theory and gear transmission physical model, and the gear mesh contact impact model was set up further. The finite element solution algorithm for solving the impact problem was given. Then, the accurate 3D model was set up based on the gear tooth surface equation, and the finite element analysis models of the meshing contact impact with different impact positions were established further. The model was to study the distribution rule of the gear surface meshing contact impact stress and relationship between the impact velocity, impact position, and the impact stress. Moreover, the reason for the maximum impact stresses distribution rule of primary and secondary impact tooth surface was discussed. Research result shows the driven wheel dangerous areas of gear root impact are the gear top of the primary impact tooth surface and the gear root of the secondary impact tooth surface; the driven wheel dangerous areas of gear top impact are the gear root of the primary impact tooth surface and gear top of the secondary impact tooth surface; the driven wheel dangerous areas of pitch circle are the gear root and pitch circle of secondary impact tooth surface; and impact velocity and impact position have a major influence on the impact stress. The study results provide a theoretical basis for the dynamic design and industrial application of CATT cylindrical gears.

scholarly journals Positive Phase Pressure Function and Pressure Attenuation Characteristic of a Liquid Carbon Dioxide Blasting System

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4134
Author(s):  
Bo Ke ◽  
Keping Zhou ◽  
Gaofeng Ren ◽  
Ji Shi ◽  
Yanan Zhang
Keyword(s):  
Phase Transition ◽  
Carbon Dioxide ◽  
High Pressure ◽  
Impact Pressure ◽  
Positive Phase ◽  
Liquid Carbon ◽  
Edge Zone ◽  
Liquid Carbon Dioxide ◽  
The Impact ◽  
Phase Pressure

As environmental requirements become more stringent, the liquid carbon dioxide blasting system is one of the non-explosive blasting technologies that, with low tensile stress energy, will replace the chemical explosive blasting technology, and the impact pressure characteristic of high-pressure fluid is a crucial factor in the process of rock breaking. To further investigate the impact and pressure attenuation characteristics of high-pressure fluid during the phase transition of liquid carbon dioxide blasting system, the pressure curves of high-pressure fluid in liquid carbon dioxide blasting systems at different distances were measured in the laboratory. Based on the mechanism analysis of phase transition kinetics, the initial jet velocity of the four experiments was calculated, and the rationality of results was verified by the Bernoulli equation. The general expression of the positive phase pressure–time function was proposed, and the idealized impact pressure curve can be divided into five stages. The impact pressure field of the liquid carbon dioxide blasting system can be divided into three areas at different distances: the explosive jet impact zone, the jet edge zone and the shock wave action zone, and the pressure–contrast distance fitting equation of the liquid carbon dioxide blasting system were obtained.

Climate-forced changes of bio-productivity of Belorussian terrestrial ecosystems

2019 ◽  
pp. 77-88
Author(s):  
S. A. Lysenko
Keyword(s):  
Climate Change ◽  
Carbon Dioxide ◽  
Vegetation Index ◽  
Precipitation Amount ◽  
Terrestrial Ecosystems ◽  
Vegetation Period ◽  
Climatic Trend ◽  
Vegetation Growth ◽  
Current Century ◽  
The Impact

The spatial and temporal particularities of Normalized Differential Vegetation Index (NDVI) changes over territory of Belarus in the current century and their relationship with climate change were investigated. The rise of NDVI is observed at approximately 84% of the Belarus area. The statistically significant growth of NDVI has exhibited at nearly 35% of the studied area (t-test at 95% confidence interval), which are mainly forests and undeveloped areas. Croplands vegetation index is largely descending. The main factor of croplands bio-productivity interannual variability is precipitation amount in vegetation period. This factor determines more than 60% of the croplands NDVI dispersion. The long-term changes of NDVI could be explained by combination of two factors: photosynthesis intensifying action of carbon dioxide and vegetation growth suppressing action of air warming with almost unchanged precipitation amount. If the observed climatic trend continues the croplands bio-productivity in many Belarus regions could be decreased at more than 20% in comparison with 2000 year. The impact of climate change on the bio-productivity of undeveloped lands is only slightly noticed on the background of its growth in conditions of rising level of carbon dioxide in the atmosphere.

scholarly journals An Examination of Green Credit Promoting Carbon Dioxide Emissions Reduction: A Provincial Panel Analysis of China

2021 ◽  
Vol 13 (13) ◽  
pp. 7148
Author(s):  
Wenjie Zhang ◽  
Mingyong Hong ◽  
Juan Li ◽  
Fuhong Li
Keyword(s):  
Carbon Dioxide ◽  
Carbon Emissions ◽  
Carbon Dioxide Emissions ◽  
Industrial Structure ◽  
Emissions Reduction ◽  
Green Finance ◽  
Carbon Emissions Reduction ◽  
Negative Effect ◽  
Emissions Intensity ◽  
The Impact

The implementation of green finance is a powerful measure to promote global carbon emissions reduction that has been highly valued by academic circles in recent years. However, the role of green credit in carbon emissions reduction in China is still lacking testing. Using a set of panel data including 30 provinces and cities, this study focused on the impact of green credit on carbon dioxide emissions in China from 2006 to 2016. The empirical results indicated that green credit has a significantly negative effect on carbon dioxide emissions intensity. Furthermore, after the mechanism examination, we found that the promotion impacts of green credit on industrial structure upgrading and technological innovation are two effective channels to help reduce carbon dioxide emissions. Heterogeneity analysis found that there are regional differences in the effect of green credit. In the western and northeastern regions, the effect of green credit is invalid. Quantile regression results implied that the greater the carbon emissions intensity, the better the effect of green credit. Finally, a further discussion revealed there exists a nonlinear correlation between green credit and carbon dioxide emissions intensity. These findings suggest that the core measures to promote carbon emission reduction in China are to continue to expand the scale of green credit, increase the technology R&D investment of enterprises, and to vigorously develop the tertiary industry.

scholarly journals Calcium phosphate phase transition in the presence of Aminosilane

2014 ◽  
Vol 70 (a1) ◽  
pp. C67-C67
Author(s):  
Babak Mostaghaci ◽  
Brigitta Loretz ◽  
Robert Haberkorn ◽  
Guido Kickelbick ◽  
Claus-Michael Lehr
Keyword(s):  
Phase Transition ◽  
Calcium Phosphate ◽  
Blood Compatibility ◽  
Transfection Efficiency ◽  
Hek293 Cells ◽  
Step Method ◽  
Calcium Phosphate Nanoparticles ◽  
Amine Groups ◽  
The Impact

Calcium phosphate has been the point of interest for in vitro gene delivery for many years because of its biocompatibility and straight forward application. However, there are some limitations regarding in vivo administration of these particles mostly because of vast agglomeration of the particles and lack of strong bond between the particles and pDNA. We introduced a simple single step method to functionalize calcium phosphate nanoparticles with Aminosilanes having a different number of amine groups. The nanoparticles were characterized chemically and structurally and their toxicity and interaction with pDNA were studied as well. Results revealed that different crystalline phase of calcium phosphate nanoparticles (Brushite and Hydroxyapatite) with a size below 150 nm were prepared, depending on conditions of synthesis and phase, each with a narrow size distribution. The aminosilane agents caused oriented nucleation and growth of crystallites and can decrease the pH for producing hydroxyapatite phase. The phenomenon could be revealed with the presence of anisotropy in the structure of synthesized hydroxyapatite. The number of amine groups in the Aminosilane agent could change the phase transition pH. Brushite particles revealed to have stronger interaction with pDNA mostly because of their higher positive surface charge. Both particles showed blood compatibility and negligible toxicity. Transfection experiment revealed the capability of both brushite and hydroxyapatite particles to transfect A549 and HEK293 cells. The new modified nanoparticles can be stored in a dried state and re-dispersed easily at the time of administration. Moreover, the transfection efficiency is higher in comparison with conventional calcium phosphate. This study showed the impact of presence and type of the modifying agent on the crystal structure and the amount of surface functionalization of nanoparticles, which in consequence influenced their interaction with cells.

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