In c-C4F8 and c-C4F8/CO2 mixtures, the swarm parameters including ionization coefficient, attachment coefficient and effective ionization coefficient were obtained at the ratio of the electric field strength to the ga...In c-C4F8 and c-C4F8/CO2 mixtures, the swarm parameters including ionization coefficient, attachment coefficient and effective ionization coefficient were obtained at the ratio of the electric field strength to the gas density between 150-550 Td by the steady-state Townsend （SST） method. Static breakdown voltages at each ratio were also measured at the SST condition. The limiting field strengths were obtained by two methods： computing the density-normalized effective ionization coefficient as a function of the overall density-reduced electric field strength; and measuring static breakdown voltages as a function of the product of gas density and electrode separation. Good agreement was obtained by these two methods, which ensures the correctness of the former method. The limiting field strengths of c-C4F8 and c-C4F8/CO2 mixtures were compared with those of pure SF6, 8F6/602 mixtures and pure c-C4F8. It is found that buffer gas CO2 does not reduce the limiting field strengths of c-C4F8 greatly, the limiting field strengths of c-C4F8/CO2 mixtures are higher than those of SF6/CO2 mixtures or even pure SF6, and so c-C4F8/CO2 mixtures are suggested to be possible substitutes for SF6.展开更多
The dielectric properties in vitro present characteristic changes along with the alteration of metabolic activities, which can be detected from tissue micro- structure. The dielectric properties of tissues are closely...The dielectric properties in vitro present characteristic changes along with the alteration of metabolic activities, which can be detected from tissue micro- structure. The dielectric properties of tissues are closely related to its viability, but the relationship remains unclear to us. This study aims to specify the relationship between dielectric parameters and microstructure of living tissues and to try to explain the influence of tissue viability on dielectric properties. Nine rabbits were studied in this experiment. The impedance spectroscopy （10 Hz-1 MHz） and microstructure were determined at different time intervals （from 5 rain to 7 h） after samples were prepared. Some characteristic parameters were extracted to analyze the relationship between them. The inactivation process characterized by the mierostrueturs could be detected by means of dielectric parameters： the microstructures had no obvious change within 30 rain a.nd cell swelling caused by osmosis led to the decrease of extracellular ion concentration, resulting in the rise of lowfrequency impedance after 30 rain. The reduction of impedance was accompanied by the expanding intercellular area and irregular cell shape caused by the gradual destruction of cell membrane.The functions between alteration rate of intercellular area and Cole-Cole model parameters were also established. There is a strong correlative relationship between dielectric properties and microstructure. The dielectric spectrum can be a rapid and innocuous method to monitor the status of tissues. In the future, it may be of great help for clinical application, especially in transplantation.展开更多
The data of d ieleclric properties of hum an tissues m ably com es from an in al tissues or hum an corpse at present U p to now, there has not been a report of dielectric properties of human living liver. This paper ...The data of d ieleclric properties of hum an tissues m ably com es from an in al tissues or hum an corpse at present U p to now, there has not been a report of dielectric properties of human living liver. This paper aims to studying the dielectric properties of hum an living liver and corn paring the results with those of an in al living liver as well as the human non-livhg liver. In vitro measurements of living and non-living livers from human and rabbitare shown in the range of 10 Hz to 100 MHz. Analysis of the conductivity, perm ittivity and characteristic param eters from the data were made. The conductivity of three kinds of liver were markedly different at low frequency： 0.06 S/m （living rabbit liver）, 0.13 S/m （living hum an liver） and 0.24 S/m （non-living hum an liver）; The Cole param eters that best characterize the liver of hum an and rabbit are RO, fc1,△R I and R ∞ ;The Cole param eters that best characterize the living and non-living liver ofhum an are RO, fc1,△R I,△R2 and R ∞. In conclusion,we can＇t substitute the dielectric properties of anin al or hum an corpse liver for the living human liver. The results suggest that the study on the dielectric properties of living hum an tissues has great sign ificance.展开更多
基金the National Natural Science Foundation of China (No. 50777041)
文摘In c-C4F8 and c-C4F8/CO2 mixtures, the swarm parameters including ionization coefficient, attachment coefficient and effective ionization coefficient were obtained at the ratio of the electric field strength to the gas density between 150-550 Td by the steady-state Townsend （SST） method. Static breakdown voltages at each ratio were also measured at the SST condition. The limiting field strengths were obtained by two methods： computing the density-normalized effective ionization coefficient as a function of the overall density-reduced electric field strength; and measuring static breakdown voltages as a function of the product of gas density and electrode separation. Good agreement was obtained by these two methods, which ensures the correctness of the former method. The limiting field strengths of c-C4F8 and c-C4F8/CO2 mixtures were compared with those of pure SF6, 8F6/602 mixtures and pure c-C4F8. It is found that buffer gas CO2 does not reduce the limiting field strengths of c-C4F8 greatly, the limiting field strengths of c-C4F8/CO2 mixtures are higher than those of SF6/CO2 mixtures or even pure SF6, and so c-C4F8/CO2 mixtures are suggested to be possible substitutes for SF6.
基金National Natural Science Foundation of Chinagrant number:50937005,61071033
文摘The dielectric properties in vitro present characteristic changes along with the alteration of metabolic activities, which can be detected from tissue micro- structure. The dielectric properties of tissues are closely related to its viability, but the relationship remains unclear to us. This study aims to specify the relationship between dielectric parameters and microstructure of living tissues and to try to explain the influence of tissue viability on dielectric properties. Nine rabbits were studied in this experiment. The impedance spectroscopy （10 Hz-1 MHz） and microstructure were determined at different time intervals （from 5 rain to 7 h） after samples were prepared. Some characteristic parameters were extracted to analyze the relationship between them. The inactivation process characterized by the mierostrueturs could be detected by means of dielectric parameters： the microstructures had no obvious change within 30 rain a.nd cell swelling caused by osmosis led to the decrease of extracellular ion concentration, resulting in the rise of lowfrequency impedance after 30 rain. The reduction of impedance was accompanied by the expanding intercellular area and irregular cell shape caused by the gradual destruction of cell membrane.The functions between alteration rate of intercellular area and Cole-Cole model parameters were also established. There is a strong correlative relationship between dielectric properties and microstructure. The dielectric spectrum can be a rapid and innocuous method to monitor the status of tissues. In the future, it may be of great help for clinical application, especially in transplantation.
基金National Natural Science Foundation of the People's Republic of Chinagrant number:50937005 and 61071033
文摘The data of d ieleclric properties of hum an tissues m ably com es from an in al tissues or hum an corpse at present U p to now, there has not been a report of dielectric properties of human living liver. This paper aims to studying the dielectric properties of hum an living liver and corn paring the results with those of an in al living liver as well as the human non-livhg liver. In vitro measurements of living and non-living livers from human and rabbitare shown in the range of 10 Hz to 100 MHz. Analysis of the conductivity, perm ittivity and characteristic param eters from the data were made. The conductivity of three kinds of liver were markedly different at low frequency： 0.06 S/m （living rabbit liver）, 0.13 S/m （living hum an liver） and 0.24 S/m （non-living hum an liver）; The Cole param eters that best characterize the liver of hum an and rabbit are RO, fc1,△R I and R ∞ ;The Cole param eters that best characterize the living and non-living liver ofhum an are RO, fc1,△R I,△R2 and R ∞. In conclusion,we can＇t substitute the dielectric properties of anin al or hum an corpse liver for the living human liver. The results suggest that the study on the dielectric properties of living hum an tissues has great sign ificance.
