42 research outputs found
The basic principle of GLCM.
CO2 blasting has been identified as a potent method for enhancing the permeability of coal seams and improving gas drainage efficiency. This study is focused on elucidating the deformation and fracture mechanisms of coal and rock during CO2 blasting and on identifying the precursor characteristics of these processes. To this end, a CO2 blasting-induced coal rock fracture pressure model and a gas pressure distribution model were developed. The research utilized a self-developed CO2 blasting test platform along with a non-contact full-strain field measurement analysis system. Briquette samples were subjected to CO2 blasting tests under controlled experimental conditions, which included an axial pressure of 1.0 MPa and variable gas pressures of 0.5, 1.0, and 1.5 MPa. This methodology enabled the capture of the principal strain field on the surface of the samples. The Gray Level Co-occurrence Matrix (GLCM) was employed to extract and analyze the grayscale and texture features of the strain cloud maps, facilitating a quantitative assessment of their evolution. The aim was to pinpoint the precursor characteristics associated with coal rock cracking and crack propagation. The results revealed that: (1) During the cracking and subsequent propagation of samples, the strain field’s grayscale histogram underwent a transformation from a “broad and low” to a “narrow and high” configuration, with a consistent increase in peak frequency. Specifically, at 3 ms, a primary crack was observed in the sample, evidenced by a grayscale peak frequency of 0.0846. By 9 ms, as the crack propagated, the grayscale peak frequency escalated to 0.1626. (2) The texture feature parameters experienced their initial abrupt change at 3ms. Correlation with the gas pressure distribution model indicated that this was the crack initiation moment in the sample. (3) A secondary abrupt shift in the texture feature parameters occurred at 9ms, in conjunction with experimental phenomena, was identified as the crack propagation phase. Monitoring the grayscale and texture features of the principal strain field on the coal rock surface proved effective in recognizing the precursor characteristics of crack initiation and propagation. This research has the potential to reduce blasting costs in coal mines, optimize blasting effects, and provided theoretical guidance for enhancing gas extraction efficiency from deep and low permeability coal seams.</div
CO<sub>2</sub> blasting test system.
CO2 blasting has been identified as a potent method for enhancing the permeability of coal seams and improving gas drainage efficiency. This study is focused on elucidating the deformation and fracture mechanisms of coal and rock during CO2 blasting and on identifying the precursor characteristics of these processes. To this end, a CO2 blasting-induced coal rock fracture pressure model and a gas pressure distribution model were developed. The research utilized a self-developed CO2 blasting test platform along with a non-contact full-strain field measurement analysis system. Briquette samples were subjected to CO2 blasting tests under controlled experimental conditions, which included an axial pressure of 1.0 MPa and variable gas pressures of 0.5, 1.0, and 1.5 MPa. This methodology enabled the capture of the principal strain field on the surface of the samples. The Gray Level Co-occurrence Matrix (GLCM) was employed to extract and analyze the grayscale and texture features of the strain cloud maps, facilitating a quantitative assessment of their evolution. The aim was to pinpoint the precursor characteristics associated with coal rock cracking and crack propagation. The results revealed that: (1) During the cracking and subsequent propagation of samples, the strain field’s grayscale histogram underwent a transformation from a “broad and low” to a “narrow and high” configuration, with a consistent increase in peak frequency. Specifically, at 3 ms, a primary crack was observed in the sample, evidenced by a grayscale peak frequency of 0.0846. By 9 ms, as the crack propagated, the grayscale peak frequency escalated to 0.1626. (2) The texture feature parameters experienced their initial abrupt change at 3ms. Correlation with the gas pressure distribution model indicated that this was the crack initiation moment in the sample. (3) A secondary abrupt shift in the texture feature parameters occurred at 9ms, in conjunction with experimental phenomena, was identified as the crack propagation phase. Monitoring the grayscale and texture features of the principal strain field on the coal rock surface proved effective in recognizing the precursor characteristics of crack initiation and propagation. This research has the potential to reduce blasting costs in coal mines, optimize blasting effects, and provided theoretical guidance for enhancing gas extraction efficiency from deep and low permeability coal seams.</div
The following is the MATLAB code for extracting texture feature parameters in RGB strain image.
The following is the MATLAB code for extracting texture feature parameters in RGB strain image.</p
Li Electrochemical Tuning of Metal Oxide for Highly Selective CO<sub>2</sub> Reduction
Engineering
active grain boundaries (GBs) in oxide-derived (OD)
electrocatalysts is critical to improve the selectivity in CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR), which is becoming
an increasingly important pathway for renewable energy storage and
usage. Different from traditional <i>in situ</i> electrochemical
reduction under CO<sub>2</sub>RR conditions, where some metal oxides
are converted into active metallic phases but with decreased GB densities,
here we introduce the Li electrochemical tuning (LiET) method to controllably
reduce the oxide precursors into interconnected ultrasmall metal nanoparticles
with enriched GBs. By using ZnO as a case study, we demonstrate that
the LiET-Zn with freshly exposed GBs exhibits a CO<sub>2</sub>-to-CO
partial current of ∼23 mA cm<sup>–2</sup> at an overpotential
of −948 mV, representing a 5-fold improvement from the OD-Zn
with GBs eliminated during the <i>in situ</i> electro-reduction
process. A maximal CO Faradaic efficiency of ∼91.1% is obtained
by LiET-Zn on glassy carbon substrate. The CO<sub>2</sub>-to-CO mechanism
and interfacial chemistry are further probed at the molecular level
by advanced <i>in situ</i> spectroelectrochemical technique,
where the reaction intermediate of carboxyl species adsorbed on LiET-Zn
surface is revealed
CoSe<sub>2</sub> Nanoparticles Grown on Carbon Fiber Paper: An Efficient and Stable Electrocatalyst for Hydrogen Evolution Reaction
Development
of a non-noble-metal hydrogen-producing catalyst is
essential to the development of solar water-splitting devices. Improving
both the activity and the stability of the catalyst remains a key
challenge. In this Communication, we describe a two-step reaction
for preparing three-dimensional electrodes composed of CoSe<sub>2</sub> nanoparticles grown on carbon fiber paper. The electrode exhibits
excellent catalytic activity for a hydrogen evolution reaction in
an acidic electrolyte (100 mA/cm<sup>2</sup> at an overpotential of
∼180 mV). Stability tests though long-term potential cycles
and extended electrolysis confirm the exceptional durability of the
catalyst. This development offers an attractive catalyst material
for large-scale water-splitting technology
Schematic diagram of sample and position of gas blast tube.
Schematic diagram of sample and position of gas blast tube.</p
The mechanical model.
CO2 blasting has been identified as a potent method for enhancing the permeability of coal seams and improving gas drainage efficiency. This study is focused on elucidating the deformation and fracture mechanisms of coal and rock during CO2 blasting and on identifying the precursor characteristics of these processes. To this end, a CO2 blasting-induced coal rock fracture pressure model and a gas pressure distribution model were developed. The research utilized a self-developed CO2 blasting test platform along with a non-contact full-strain field measurement analysis system. Briquette samples were subjected to CO2 blasting tests under controlled experimental conditions, which included an axial pressure of 1.0 MPa and variable gas pressures of 0.5, 1.0, and 1.5 MPa. This methodology enabled the capture of the principal strain field on the surface of the samples. The Gray Level Co-occurrence Matrix (GLCM) was employed to extract and analyze the grayscale and texture features of the strain cloud maps, facilitating a quantitative assessment of their evolution. The aim was to pinpoint the precursor characteristics associated with coal rock cracking and crack propagation. The results revealed that: (1) During the cracking and subsequent propagation of samples, the strain field’s grayscale histogram underwent a transformation from a “broad and low” to a “narrow and high” configuration, with a consistent increase in peak frequency. Specifically, at 3 ms, a primary crack was observed in the sample, evidenced by a grayscale peak frequency of 0.0846. By 9 ms, as the crack propagated, the grayscale peak frequency escalated to 0.1626. (2) The texture feature parameters experienced their initial abrupt change at 3ms. Correlation with the gas pressure distribution model indicated that this was the crack initiation moment in the sample. (3) A secondary abrupt shift in the texture feature parameters occurred at 9ms, in conjunction with experimental phenomena, was identified as the crack propagation phase. Monitoring the grayscale and texture features of the principal strain field on the coal rock surface proved effective in recognizing the precursor characteristics of crack initiation and propagation. This research has the potential to reduce blasting costs in coal mines, optimize blasting effects, and provided theoretical guidance for enhancing gas extraction efficiency from deep and low permeability coal seams.</div
Texture feature parameters-time curve of the CO<sub>2</sub> blasting process.
Texture feature parameters-time curve of the CO2 blasting process.</p
Relationship between pressure and time under different initial gas pressures.
Relationship between pressure and time under different initial gas pressures.</p
Physical and mechanical parameters.
CO2 blasting has been identified as a potent method for enhancing the permeability of coal seams and improving gas drainage efficiency. This study is focused on elucidating the deformation and fracture mechanisms of coal and rock during CO2 blasting and on identifying the precursor characteristics of these processes. To this end, a CO2 blasting-induced coal rock fracture pressure model and a gas pressure distribution model were developed. The research utilized a self-developed CO2 blasting test platform along with a non-contact full-strain field measurement analysis system. Briquette samples were subjected to CO2 blasting tests under controlled experimental conditions, which included an axial pressure of 1.0 MPa and variable gas pressures of 0.5, 1.0, and 1.5 MPa. This methodology enabled the capture of the principal strain field on the surface of the samples. The Gray Level Co-occurrence Matrix (GLCM) was employed to extract and analyze the grayscale and texture features of the strain cloud maps, facilitating a quantitative assessment of their evolution. The aim was to pinpoint the precursor characteristics associated with coal rock cracking and crack propagation. The results revealed that: (1) During the cracking and subsequent propagation of samples, the strain field’s grayscale histogram underwent a transformation from a “broad and low” to a “narrow and high” configuration, with a consistent increase in peak frequency. Specifically, at 3 ms, a primary crack was observed in the sample, evidenced by a grayscale peak frequency of 0.0846. By 9 ms, as the crack propagated, the grayscale peak frequency escalated to 0.1626. (2) The texture feature parameters experienced their initial abrupt change at 3ms. Correlation with the gas pressure distribution model indicated that this was the crack initiation moment in the sample. (3) A secondary abrupt shift in the texture feature parameters occurred at 9ms, in conjunction with experimental phenomena, was identified as the crack propagation phase. Monitoring the grayscale and texture features of the principal strain field on the coal rock surface proved effective in recognizing the precursor characteristics of crack initiation and propagation. This research has the potential to reduce blasting costs in coal mines, optimize blasting effects, and provided theoretical guidance for enhancing gas extraction efficiency from deep and low permeability coal seams.</div