A temperature-controlled and pressure-controlled coaxial dielectric barrier discharge （DBD） reactor was developed to decouple the thermal and kinetic effects of radio frequency （RF） discharge on methane conversion...A temperature-controlled and pressure-controlled coaxial dielectric barrier discharge （DBD） reactor was developed to decouple the thermal and kinetic effects of radio frequency （RF） discharge on methane conversion, and further to compare the kinetic behaviors of the mechanistically similar reactions of methane conversion with O2 and CO2 additives. A kinetic mechanism for RF plasma assisted methane conversion was assembled. The formation of products in the RF plasma reactor was measured with Gas Chromatography （GC-TCD） and the data were used to validate the kinetic model. The experimental and computational results showed the different kinetic roles of carbon dioxide and oxygen additives in methane conversion, due to the different dissociation and ionization energy of the two additive gases, as well as the thus produced electron energy distribution function （EEDF）. Fuel oxidation by plasma generated O, O（1D）, O2（a1△Ag）, O2（b1∑＋g） and O＋ in partial oxidation of methane was observed essential for methane consumption, which resulted in an increase in methane conversion rate, compared to pure methane pyrolysis and dry reforming of methane with CO2 additive. It was also found that dry reforming of methane with CO2 was by far the easier to produce the syngas as well as C2 hydrocarbon species, due to the weak oxidation ability of CO2 and also the significant deposition of the electron energy on CH4 disso- ciation in a dry reforming discharge mixture. This kinetic study produced comparative data to demonstrate the contribution of CO2/O2 additive in non-eauilibrium plasma assisted methane conversion.展开更多
Objective: To describe the characteristic appearance of cavernous hemangioma of the liver (CHL) presented in carbon dioxide digital subtraction angiography (CO2-DSA) and to evaluate the significance of CO2-DSA in the ...Objective: To describe the characteristic appearance of cavernous hemangioma of the liver (CHL) presented in carbon dioxide digital subtraction angiography (CO2-DSA) and to evaluate the significance of CO2-DSA in the diagnosis of CHL. Methods: Both CO2-DSA and iodinated contrast DSA (IC-DSA) were performed in all 16 patients with CHL, and the angiographic manifestations in the same patients were compared. The image quality was rated by three experienced angiographers, and the complications were also assessed. Results: There was good correlation between angiographers on image quality (R = 0. 73). Diagnostic images were obtained with both CO2-DSA and IC-DSA in all CHL patients. No difference was noted between IC-DSA and CO2-DSA in visualizing the proper hepatic arteries and its branches (P>0. 05). CO2-DSA produced better images that clearly described the tumor size, shape and margination than those by IC-DSA (P< 0. 05), but both demonstrated characteristic appearances of early opacification and persistent contrast enhancement of the tumors. The portal vein branches near the tumors were constantly demonstrated by CO2-DSA in 15 cases (15/16) but only in 2 cases (2/16) by IC-DSA. Conclusion: CO2-DSA is sensitive in CHL diagnosis, and in patients with contraindications to IC or with unsatisfactory imaging results by IC-DSA, CO2-DSA is a good alternative. As show in most cases by CO2-DSA, the portal veins might act as the main drainage vein of CHLs.展开更多
基金Supported by the National Natural Science Foundation of China(51376021,21676024)
文摘A temperature-controlled and pressure-controlled coaxial dielectric barrier discharge （DBD） reactor was developed to decouple the thermal and kinetic effects of radio frequency （RF） discharge on methane conversion, and further to compare the kinetic behaviors of the mechanistically similar reactions of methane conversion with O2 and CO2 additives. A kinetic mechanism for RF plasma assisted methane conversion was assembled. The formation of products in the RF plasma reactor was measured with Gas Chromatography （GC-TCD） and the data were used to validate the kinetic model. The experimental and computational results showed the different kinetic roles of carbon dioxide and oxygen additives in methane conversion, due to the different dissociation and ionization energy of the two additive gases, as well as the thus produced electron energy distribution function （EEDF）. Fuel oxidation by plasma generated O, O（1D）, O2（a1△Ag）, O2（b1∑＋g） and O＋ in partial oxidation of methane was observed essential for methane consumption, which resulted in an increase in methane conversion rate, compared to pure methane pyrolysis and dry reforming of methane with CO2 additive. It was also found that dry reforming of methane with CO2 was by far the easier to produce the syngas as well as C2 hydrocarbon species, due to the weak oxidation ability of CO2 and also the significant deposition of the electron energy on CH4 disso- ciation in a dry reforming discharge mixture. This kinetic study produced comparative data to demonstrate the contribution of CO2/O2 additive in non-eauilibrium plasma assisted methane conversion.
文摘Objective: To describe the characteristic appearance of cavernous hemangioma of the liver (CHL) presented in carbon dioxide digital subtraction angiography (CO2-DSA) and to evaluate the significance of CO2-DSA in the diagnosis of CHL. Methods: Both CO2-DSA and iodinated contrast DSA (IC-DSA) were performed in all 16 patients with CHL, and the angiographic manifestations in the same patients were compared. The image quality was rated by three experienced angiographers, and the complications were also assessed. Results: There was good correlation between angiographers on image quality (R = 0. 73). Diagnostic images were obtained with both CO2-DSA and IC-DSA in all CHL patients. No difference was noted between IC-DSA and CO2-DSA in visualizing the proper hepatic arteries and its branches (P>0. 05). CO2-DSA produced better images that clearly described the tumor size, shape and margination than those by IC-DSA (P< 0. 05), but both demonstrated characteristic appearances of early opacification and persistent contrast enhancement of the tumors. The portal vein branches near the tumors were constantly demonstrated by CO2-DSA in 15 cases (15/16) but only in 2 cases (2/16) by IC-DSA. Conclusion: CO2-DSA is sensitive in CHL diagnosis, and in patients with contraindications to IC or with unsatisfactory imaging results by IC-DSA, CO2-DSA is a good alternative. As show in most cases by CO2-DSA, the portal veins might act as the main drainage vein of CHLs.
