We experimentally studied the effect of crack aperture on P-wave velocity, amplitude, anisotropy and dispersion. Experimental models were constructed based on Hudson＇s theory. Six crack models were embedded with equa...We experimentally studied the effect of crack aperture on P-wave velocity, amplitude, anisotropy and dispersion. Experimental models were constructed based on Hudson＇s theory. Six crack models were embedded with equal-radius penny-shaped crack inclusions in each layer. The P-wave velocity and amplitude were measured parallel and perpendicular to the layers of cracks at frequencies of 0.1 MHz to 1 MHz. The experiments show that as the crack aperture increases from 0.l mm to 0.34 mm, the amplitude of the P-waves parallel to the crack layers decreases linearly with increasing frequency and the P-wave velocity dispersion varies from 1.5% to 2.1%, whereas the amplitude of the P-wave perpendicular to the crack layers decreases quadratically with increasing frequency and the velocity dispersion varies from 1.9% to 4.7%. The variation in the velocity dispersion parallel and perpendicular to the cracks intensifies the anisotropy dispersion of the P-waves in the crack models （6.7% to 83%）. The P-wave dispersion strongly depends on the scattering characteristics of the crack apertures.展开更多
CO2 sorption and diffusion in coal are closely related to the occurrence of coal and gas outburst,geological sequestration of CO2 in coalbeds,and enhancing coalbed methane recovery by injecting CO2.Hence,it is signifi...CO2 sorption and diffusion in coal are closely related to the occurrence of coal and gas outburst,geological sequestration of CO2 in coalbeds,and enhancing coalbed methane recovery by injecting CO2.Hence,it is significant to investigate the sorption properties and diffusion models of CO2 in coal.Here we used a newly designed experimental apparatus at Peking University to investigate the sorption and diffusion properties of CO2 in natural coal samples from Dashucun Mine and Wutongzhuang Mine in Handan city,Hebei province,and Jinhuagong Mine in Datong city,Shanxi province,and obtained CO2 sorption isotherms and diffusivity models.The results indicate that,in a certain pressure range,CO2 sorption isotherms for the coal samples are consistent with the Langmuir model,which assumes that monolayer sorption occurs at the interface between coal matrix and CO2 molecules,and the sorption isotherms feature nonstandard hyperbolas in mathematics.At the same pressure and temperature,as the vitrinite content increases,coal adsorbs more CO2 molecules.The relation between the sorption capacity and the coal rank may be described as a "U-type" trend,and medium rank coal has the least sorption capacity.The bulk diffusivity of CO2 in coal is not constant;in the range of CO2 mass fraction greater than 1%,it increases roughly linearly with increasing mass fraction of CO2 adsorbed(or CO2 partial pressure) in coal.CO2 diffusivity in coal is approximately 10-4 to 10-2 mm2/s in magnitudes,and the diffusivity ranges in coal samples are 3×10-4 to 8×10-3 mm2/s from Dashucun Mine,2×10-4 to 4×10-3 mm2/s from Wutongzhuang Mine,and 2×10-4 to 4×10-3 mm2/s from Jinhuagong Mine.The results of the CO2 sorption and diffusion study can be applied to help predict and prevent coal and gas outburst as well as to evaluate the feasibility in geological sequestration of CO2 and to enhance coalbed methane recovery.展开更多
In the present paper, the elastic scattering of6 Li + 209 Bi system is reanalyzed by using the double folding model (DFM) at energies near the Coulomb barrier (ELab=29.9 and 32.8 MeV). With this goal, a new density di...In the present paper, the elastic scattering of6 Li + 209 Bi system is reanalyzed by using the double folding model (DFM) at energies near the Coulomb barrier (ELab=29.9 and 32.8 MeV). With this goal, a new density distribution of6 Li nucleus, the no-core full configuration (NCFC) density distribution (DD), is used to obtain the real potentials in DFM calculations. The NCFC DD results are compared with the results of both gaussian shape (GS) DD and an earlier study as well as the experimental data. This comparison provides information about the similarities and differences of the models used in calculations.展开更多
基金supported by the Major National Project Program (No.2011ZX05007-006)
文摘We experimentally studied the effect of crack aperture on P-wave velocity, amplitude, anisotropy and dispersion. Experimental models were constructed based on Hudson＇s theory. Six crack models were embedded with equal-radius penny-shaped crack inclusions in each layer. The P-wave velocity and amplitude were measured parallel and perpendicular to the layers of cracks at frequencies of 0.1 MHz to 1 MHz. The experiments show that as the crack aperture increases from 0.l mm to 0.34 mm, the amplitude of the P-waves parallel to the crack layers decreases linearly with increasing frequency and the P-wave velocity dispersion varies from 1.5% to 2.1%, whereas the amplitude of the P-wave perpendicular to the crack layers decreases quadratically with increasing frequency and the velocity dispersion varies from 1.9% to 4.7%. The variation in the velocity dispersion parallel and perpendicular to the cracks intensifies the anisotropy dispersion of the P-waves in the crack models （6.7% to 83%）. The P-wave dispersion strongly depends on the scattering characteristics of the crack apertures.
基金supported by Peking University (985 Program by Chinese Ministry of Education)the National Natural Science Foundation of China (Grant No.40640420141)
文摘CO2 sorption and diffusion in coal are closely related to the occurrence of coal and gas outburst,geological sequestration of CO2 in coalbeds,and enhancing coalbed methane recovery by injecting CO2.Hence,it is significant to investigate the sorption properties and diffusion models of CO2 in coal.Here we used a newly designed experimental apparatus at Peking University to investigate the sorption and diffusion properties of CO2 in natural coal samples from Dashucun Mine and Wutongzhuang Mine in Handan city,Hebei province,and Jinhuagong Mine in Datong city,Shanxi province,and obtained CO2 sorption isotherms and diffusivity models.The results indicate that,in a certain pressure range,CO2 sorption isotherms for the coal samples are consistent with the Langmuir model,which assumes that monolayer sorption occurs at the interface between coal matrix and CO2 molecules,and the sorption isotherms feature nonstandard hyperbolas in mathematics.At the same pressure and temperature,as the vitrinite content increases,coal adsorbs more CO2 molecules.The relation between the sorption capacity and the coal rank may be described as a "U-type" trend,and medium rank coal has the least sorption capacity.The bulk diffusivity of CO2 in coal is not constant;in the range of CO2 mass fraction greater than 1%,it increases roughly linearly with increasing mass fraction of CO2 adsorbed(or CO2 partial pressure) in coal.CO2 diffusivity in coal is approximately 10-4 to 10-2 mm2/s in magnitudes,and the diffusivity ranges in coal samples are 3×10-4 to 8×10-3 mm2/s from Dashucun Mine,2×10-4 to 4×10-3 mm2/s from Wutongzhuang Mine,and 2×10-4 to 4×10-3 mm2/s from Jinhuagong Mine.The results of the CO2 sorption and diffusion study can be applied to help predict and prevent coal and gas outburst as well as to evaluate the feasibility in geological sequestration of CO2 and to enhance coalbed methane recovery.
文摘In the present paper, the elastic scattering of6 Li + 209 Bi system is reanalyzed by using the double folding model (DFM) at energies near the Coulomb barrier (ELab=29.9 and 32.8 MeV). With this goal, a new density distribution of6 Li nucleus, the no-core full configuration (NCFC) density distribution (DD), is used to obtain the real potentials in DFM calculations. The NCFC DD results are compared with the results of both gaussian shape (GS) DD and an earlier study as well as the experimental data. This comparison provides information about the similarities and differences of the models used in calculations.
