A proposed concept of outburst initiation examines the release of a large amount of gas from coal seams resulted from disintegrating thermodynamically unstable coal organic matter(COM).A coal microstructure is assumed...A proposed concept of outburst initiation examines the release of a large amount of gas from coal seams resulted from disintegrating thermodynamically unstable coal organic matter(COM).A coal microstructure is assumed to getting unstable due to shear component appearance triggered by mining operations and tectonic activities considered as the primary factor while COM disintegration under the impact of weak electric fields can be defined as a secondary one.The energy of elastic deformations stored in the coal microstructure activates chemical reactions to tilt the energy balance in a“coal–gas”system.Based on this concept a mathematical model of a gas flow in the coal where porosity and permeability are changed due to chemical reactions has been developed.Using this model we calculated gas pressure changes in the pores initiated by gas release near the working face till satisfying force and energy criteria of outburst.The simulation results demonstrated forming overpressure zone in the area of intensive gas release with enhanced porosity and permeability.The calculated outburst parameters are well combined with those evaluated by field measurements.展开更多
Into the study of quasi-relaxation, in the past researches it has been concluded that the condition of meta-stability in the metallic specimen is given by the plasticity explained by the plastic energy in the process ...Into the study of quasi-relaxation, in the past researches it has been concluded that the condition of meta-stability in the metallic specimen is given by the plasticity explained by the plastic energy in the process of the quasi-relaxation. It is calculated through quasi-relaxation functional of this energy to obtain a spectra in the space D(σ – ε;t), that induces the existence of functions φ(t), and Ψ(t), related with the fundamental curves of quasi-relaxation given by σ(t), with their poles in , which is got in the maximum of stress given by σ0 = σ1. Also the tensor of plastic deformation that represents the plastic load during the application of specimen machine, cannot be obtained without poles in the space D(σ;t), corresponding the curves calculated into the space D(σ – ε;t), by curves that in the kinetic process of quasi-relaxation are represented by experimental curves in coordinates log σ – t. This situation cannot be eluded, since in this phenomena exist dislocations that go conform fatigue in the nano-crystalline structure of metals. From this point of view, is necessary to obtain a spectral study related to the energy using functions that permits the modeling and compute the states of quasi-relaxation included in the poles in the deformation problem to complete the solutions in the space D(σ – ε;t), and try a new method of solution of the differential equations of the quasi-relaxation analysis. In a nearly future development, the information obtained by this spectral study (by our integral transforms), will be able to give place to the programming through the spectral encoding of the materials in the meta-stability state, which is propitious to a nano-technological transformation of materials, concrete case, some metals.展开更多
Starting with the stoichiometric and highly homogeneous gel-precursor,single-phase metastable melilite La_(2)Ga_(3)O_(7.5),as the end-member of solid solution La_(1+x)Sr_(1−x)Ga_(3)O_(7+x/2)(0≤x≤1),has been synthesi...Starting with the stoichiometric and highly homogeneous gel-precursor,single-phase metastable melilite La_(2)Ga_(3)O_(7.5),as the end-member of solid solution La_(1+x)Sr_(1−x)Ga_(3)O_(7+x/2)(0≤x≤1),has been synthesized by solid-state reaction at 700℃ for 2 h via a kinetically favorable mechanism and characterized by X-ray diffraction(XRD),Raman,X-ray photoelectron spectroscopy(XPS),field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),AC impedance spectroscopy,etc.It has been revealed that the as-synthesized melilite La_(2)Ga_(3)O_(7.5) shows an orthorhombic symmetry with crystal cell parameters a=11.4690(1)A,b=11.2825(4)A,and c=10.3735(4)A,while has more Raman active modes than LaSrGa_(3)O_(7) with a tetragonal structure,which was also synthesized under the same conditions for comparison,but tends to slowly decompose into perovskite LaGaO_(3) and Ga2O_(3) when annealed at 700℃ for over 20 h driven by its meta-stability.Moreover,the metastable La2Ga3O7.5 shows a higher XPS binding energy for the excess oxide ions in the crystal structure than those at normal lattice sites.Its intrinsic grain oxide ion conductivity can reach as high as 0.04 and 0.51 mS·cm^(-1) at 550 and 700℃,respectively,characterized by a simple Arrhenius relationship ln(σT)-1/T with invariable activation energy,E_(a)=1.22 eV,over the temperature range from 300 to 700℃,along with an apparent grain boundary conductivity that is about double that from the grains thanks to the clean grain boundaries.This paper provides a new strategic approach to the synthesis of complex oxides that may be of high performance but are difficultly achieved by the conventional ceramic method at high temperatures.展开更多
基金the Ministry of Education and Science of Ukraine(No.0117U001129).
文摘A proposed concept of outburst initiation examines the release of a large amount of gas from coal seams resulted from disintegrating thermodynamically unstable coal organic matter(COM).A coal microstructure is assumed to getting unstable due to shear component appearance triggered by mining operations and tectonic activities considered as the primary factor while COM disintegration under the impact of weak electric fields can be defined as a secondary one.The energy of elastic deformations stored in the coal microstructure activates chemical reactions to tilt the energy balance in a“coal–gas”system.Based on this concept a mathematical model of a gas flow in the coal where porosity and permeability are changed due to chemical reactions has been developed.Using this model we calculated gas pressure changes in the pores initiated by gas release near the working face till satisfying force and energy criteria of outburst.The simulation results demonstrated forming overpressure zone in the area of intensive gas release with enhanced porosity and permeability.The calculated outburst parameters are well combined with those evaluated by field measurements.
文摘Into the study of quasi-relaxation, in the past researches it has been concluded that the condition of meta-stability in the metallic specimen is given by the plasticity explained by the plastic energy in the process of the quasi-relaxation. It is calculated through quasi-relaxation functional of this energy to obtain a spectra in the space D(σ – ε;t), that induces the existence of functions φ(t), and Ψ(t), related with the fundamental curves of quasi-relaxation given by σ(t), with their poles in , which is got in the maximum of stress given by σ0 = σ1. Also the tensor of plastic deformation that represents the plastic load during the application of specimen machine, cannot be obtained without poles in the space D(σ;t), corresponding the curves calculated into the space D(σ – ε;t), by curves that in the kinetic process of quasi-relaxation are represented by experimental curves in coordinates log σ – t. This situation cannot be eluded, since in this phenomena exist dislocations that go conform fatigue in the nano-crystalline structure of metals. From this point of view, is necessary to obtain a spectral study related to the energy using functions that permits the modeling and compute the states of quasi-relaxation included in the poles in the deformation problem to complete the solutions in the space D(σ – ε;t), and try a new method of solution of the differential equations of the quasi-relaxation analysis. In a nearly future development, the information obtained by this spectral study (by our integral transforms), will be able to give place to the programming through the spectral encoding of the materials in the meta-stability state, which is propitious to a nano-technological transformation of materials, concrete case, some metals.
基金supported by the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions,China.
文摘Starting with the stoichiometric and highly homogeneous gel-precursor,single-phase metastable melilite La_(2)Ga_(3)O_(7.5),as the end-member of solid solution La_(1+x)Sr_(1−x)Ga_(3)O_(7+x/2)(0≤x≤1),has been synthesized by solid-state reaction at 700℃ for 2 h via a kinetically favorable mechanism and characterized by X-ray diffraction(XRD),Raman,X-ray photoelectron spectroscopy(XPS),field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),AC impedance spectroscopy,etc.It has been revealed that the as-synthesized melilite La_(2)Ga_(3)O_(7.5) shows an orthorhombic symmetry with crystal cell parameters a=11.4690(1)A,b=11.2825(4)A,and c=10.3735(4)A,while has more Raman active modes than LaSrGa_(3)O_(7) with a tetragonal structure,which was also synthesized under the same conditions for comparison,but tends to slowly decompose into perovskite LaGaO_(3) and Ga2O_(3) when annealed at 700℃ for over 20 h driven by its meta-stability.Moreover,the metastable La2Ga3O7.5 shows a higher XPS binding energy for the excess oxide ions in the crystal structure than those at normal lattice sites.Its intrinsic grain oxide ion conductivity can reach as high as 0.04 and 0.51 mS·cm^(-1) at 550 and 700℃,respectively,characterized by a simple Arrhenius relationship ln(σT)-1/T with invariable activation energy,E_(a)=1.22 eV,over the temperature range from 300 to 700℃,along with an apparent grain boundary conductivity that is about double that from the grains thanks to the clean grain boundaries.This paper provides a new strategic approach to the synthesis of complex oxides that may be of high performance but are difficultly achieved by the conventional ceramic method at high temperatures.
