The nonlinear J-E characteristics under self-heating equilibrium for conductive composites based on high density polyethylene were studied. The results show that there are identical conduction mechanisms under self-he...The nonlinear J-E characteristics under self-heating equilibrium for conductive composites based on high density polyethylene were studied. The results show that there are identical conduction mechanisms under self-heating equilibrium for the composites with various initial resistivities determined by filler content or ambient temperature. The nonlinear conduction behavior was involved in the limited microstructure transformations of the conducting network induced by electrical field applied and the corresponding self-heating effect. A reversible thermal fuse (RTF) model was suggested to interpret the physical origin of the nonlinear J-E characteristics.展开更多
The dc conductivity in vacuum evaporated amorphous thin films of the glassy alloys Se100–xZnx(2 ≤ x ≤ 20) are meas-ured in the temperature range (308 - 388 K). The dc conductivity (σdc) is increases with increased...The dc conductivity in vacuum evaporated amorphous thin films of the glassy alloys Se100–xZnx(2 ≤ x ≤ 20) are meas-ured in the temperature range (308 - 388 K). The dc conductivity (σdc) is increases with increased of Zn concentration in the glassy alloys. The activation energy (ΔE) decreases with increase of Zn content. The conduction is explained on the basis of localized state in the mobility gap. To study the effect of electric field, a Current-Voltage characteristic has been measured at various fixed temperatures. The Current-Voltage data are fitted into the theory of space charge limited conduction in case of uniform distribution of traps in mobility gap at high electric fields (E ~104 V/cm) of these materials. The density of localized state (g0) are estimated by fitting in theory of space charge limited conduction (SCLC) at the temperature range of (352 - 372 K) in the glassy Se100–xZnx. The density of localized state (0) near the Fermi level are increases with increase of Zn concentration in the (Se100–xZnx) thin films and explain on the basis of increase of the Zn-Se bond.展开更多
Irradiation effects of γ-radiation on the physical and electrical properties of polycarbonate (Makrofol-E( film has been studied to be able to investigate the dielectric response of irradiated polymers for a wide ran...Irradiation effects of γ-radiation on the physical and electrical properties of polycarbonate (Makrofol-E( film has been studied to be able to investigate the dielectric response of irradiated polymers for a wide range of fluence and frequency. The dielectric constant (ε') The loss tangent (tanδ), dielectric loss factor (ε''), the a.c electrical conductivity (σ) and the relaxation time (τ), were measured in the frequency range from (40) Hz to (4) MHz. These samples were irradiated by means of γ-rays from 10 up to 200 KGy. The change in different properties as a function of absorbed dose was studied. Degradation of the polymers leading to amorphisation was observed by increasing the absorbed γ- dose. The induced changes in the electrical conductivity due to γ-rays irradiation of Makrofol-E provide a better method for γ -dose measurements. A semi-empirical equation was developed to use Makrofol-E as a dielectric dosimeter. Furthermore, Makrofol-E has much greater resistance to radiation damage;the attained results suggested strongly the applicability of Makrofol-E to be used in medical products applications.展开更多
Previous studies have shown that ulnar nerve compound muscle action potential recorded by the conventional“belly-tendon”montage does not accurately and completely reflect the action potential of the ulnar nerve domi...Previous studies have shown that ulnar nerve compound muscle action potential recorded by the conventional“belly-tendon”montage does not accurately and completely reflect the action potential of the ulnar nerve dominating the abductor digiti minimi muscle due to the effects of far-field potentials of intrinsic hand muscles.A new method of ulnar nerve compound muscle action potential measurement was developed in 2020,which adjusts the E2 electrode from the distal tendon of the abductor digitorum to the middle of the back of the proximal wrist.This new method may reduce the influence of the reference electrode and better reflect the actual ulnar nerve compound muscle action potential.In this prospective cross-sectional study,we included 64 patients with amyotrophic lateral sclerosis and 64 age-and sex-matched controls who underwent conventional and novel ulnar nerve compound muscle action potential measurement between April 2020 and May 2021 in Peking University Third Hospital.The compound muscle action potential waveforms recorded by the new montage were unimodal and more uniform than those recorded by traditional montage.In the controls,no significant difference in the compound muscle action potential waveforms was found between the traditional montage and new montage recordings.In amyotrophic lateral sclerosis patients presenting with abductor digiti minimi spontaneous activity and muscular atrophy,the amplitude of compound muscle action potential-pE2 was significantly lower than that of compound muscle action potential-dE2(P<0.01).Using the new method,damaged axons were more likely to exhibit more severe amplitude decreases than those measured with the traditional method,in particular for patients in early stage amyotrophic lateral sclerosis.In addition,the decline in compound muscle action potential amplitude measured by the new method was correlated with a decrease in Revised Amyotrophic Lateral Sclerosis Functional Rating Scale scores.These findings suggest that the new ulnar nerve compound muscle action potential measurement montage reduces the effects of the reference electrode through altering the E2 electrode position,and that this method is more suitable for monitoring disease progression than the traditional montage.This method may be useful as a biomarker for longitudinal follow-up and clinical trials in amyotrophic lateral sclerosis.展开更多
Data from July 2006 to June 2008 observed at SACOL （Semi-Arid Climate and Environment Observatory of Lanzhou University, 35.946°N, 104.137°E, elev. 1961 m）, a semi-arid site in Northwest China, are used to...Data from July 2006 to June 2008 observed at SACOL （Semi-Arid Climate and Environment Observatory of Lanzhou University, 35.946°N, 104.137°E, elev. 1961 m）, a semi-arid site in Northwest China, are used to study seasonal variability of soil moisture, along with surface albedo and other soil thermal parameters, such as heat capacity, thermal conductivity and thermal diffusivity, and their relationships to soil moisture content. The results indicate that surface albedo decreases with increases in soil moisture content, showing a typical exponential relation between the surface albedo and the soil moisture. The heat capacity, the soil thermal diffusivity, and soil thermal conductivity show large variations between Julian day 90-212 and 450-578. The soil thermal conductivity is found to increase as a power function of soil moisture. Soil heat capacity and soil thermal diffusivity increase with increases in soil moisture. The SACOL observed soil moisture are also used to validate the AMSR-E/AQUA retrieved soil moisture and there is good agreement between them. The analysis of the relationship between satellite retrieved soil moisture and precipitation suggests that the variability of soil moisture depends on the variation of precipitation over the Loess Plateau.展开更多
基金the National Advanced Material Committee of China (NAMCC)，国家自然科学基金
文摘The nonlinear J-E characteristics under self-heating equilibrium for conductive composites based on high density polyethylene were studied. The results show that there are identical conduction mechanisms under self-heating equilibrium for the composites with various initial resistivities determined by filler content or ambient temperature. The nonlinear conduction behavior was involved in the limited microstructure transformations of the conducting network induced by electrical field applied and the corresponding self-heating effect. A reversible thermal fuse (RTF) model was suggested to interpret the physical origin of the nonlinear J-E characteristics.
文摘The dc conductivity in vacuum evaporated amorphous thin films of the glassy alloys Se100–xZnx(2 ≤ x ≤ 20) are meas-ured in the temperature range (308 - 388 K). The dc conductivity (σdc) is increases with increased of Zn concentration in the glassy alloys. The activation energy (ΔE) decreases with increase of Zn content. The conduction is explained on the basis of localized state in the mobility gap. To study the effect of electric field, a Current-Voltage characteristic has been measured at various fixed temperatures. The Current-Voltage data are fitted into the theory of space charge limited conduction in case of uniform distribution of traps in mobility gap at high electric fields (E ~104 V/cm) of these materials. The density of localized state (g0) are estimated by fitting in theory of space charge limited conduction (SCLC) at the temperature range of (352 - 372 K) in the glassy Se100–xZnx. The density of localized state (0) near the Fermi level are increases with increase of Zn concentration in the (Se100–xZnx) thin films and explain on the basis of increase of the Zn-Se bond.
文摘Irradiation effects of γ-radiation on the physical and electrical properties of polycarbonate (Makrofol-E( film has been studied to be able to investigate the dielectric response of irradiated polymers for a wide range of fluence and frequency. The dielectric constant (ε') The loss tangent (tanδ), dielectric loss factor (ε''), the a.c electrical conductivity (σ) and the relaxation time (τ), were measured in the frequency range from (40) Hz to (4) MHz. These samples were irradiated by means of γ-rays from 10 up to 200 KGy. The change in different properties as a function of absorbed dose was studied. Degradation of the polymers leading to amorphisation was observed by increasing the absorbed γ- dose. The induced changes in the electrical conductivity due to γ-rays irradiation of Makrofol-E provide a better method for γ -dose measurements. A semi-empirical equation was developed to use Makrofol-E as a dielectric dosimeter. Furthermore, Makrofol-E has much greater resistance to radiation damage;the attained results suggested strongly the applicability of Makrofol-E to be used in medical products applications.
基金supported by the National Natural Science Foundation of China,Nos.81873784,82071426Clinical Cohort Construction Program of Peking University Third Hospital,No.BYSYDL2019002(all to DSF)。
文摘Previous studies have shown that ulnar nerve compound muscle action potential recorded by the conventional“belly-tendon”montage does not accurately and completely reflect the action potential of the ulnar nerve dominating the abductor digiti minimi muscle due to the effects of far-field potentials of intrinsic hand muscles.A new method of ulnar nerve compound muscle action potential measurement was developed in 2020,which adjusts the E2 electrode from the distal tendon of the abductor digitorum to the middle of the back of the proximal wrist.This new method may reduce the influence of the reference electrode and better reflect the actual ulnar nerve compound muscle action potential.In this prospective cross-sectional study,we included 64 patients with amyotrophic lateral sclerosis and 64 age-and sex-matched controls who underwent conventional and novel ulnar nerve compound muscle action potential measurement between April 2020 and May 2021 in Peking University Third Hospital.The compound muscle action potential waveforms recorded by the new montage were unimodal and more uniform than those recorded by traditional montage.In the controls,no significant difference in the compound muscle action potential waveforms was found between the traditional montage and new montage recordings.In amyotrophic lateral sclerosis patients presenting with abductor digiti minimi spontaneous activity and muscular atrophy,the amplitude of compound muscle action potential-pE2 was significantly lower than that of compound muscle action potential-dE2(P<0.01).Using the new method,damaged axons were more likely to exhibit more severe amplitude decreases than those measured with the traditional method,in particular for patients in early stage amyotrophic lateral sclerosis.In addition,the decline in compound muscle action potential amplitude measured by the new method was correlated with a decrease in Revised Amyotrophic Lateral Sclerosis Functional Rating Scale scores.These findings suggest that the new ulnar nerve compound muscle action potential measurement montage reduces the effects of the reference electrode through altering the E2 electrode position,and that this method is more suitable for monitoring disease progression than the traditional montage.This method may be useful as a biomarker for longitudinal follow-up and clinical trials in amyotrophic lateral sclerosis.
基金supported bythe National Natural Science Foundation of China un-der Grants Nos40725015 and 40633017the Na-tional Basic Research Program of China under Grant No2006CB400501
文摘Data from July 2006 to June 2008 observed at SACOL （Semi-Arid Climate and Environment Observatory of Lanzhou University, 35.946°N, 104.137°E, elev. 1961 m）, a semi-arid site in Northwest China, are used to study seasonal variability of soil moisture, along with surface albedo and other soil thermal parameters, such as heat capacity, thermal conductivity and thermal diffusivity, and their relationships to soil moisture content. The results indicate that surface albedo decreases with increases in soil moisture content, showing a typical exponential relation between the surface albedo and the soil moisture. The heat capacity, the soil thermal diffusivity, and soil thermal conductivity show large variations between Julian day 90-212 and 450-578. The soil thermal conductivity is found to increase as a power function of soil moisture. Soil heat capacity and soil thermal diffusivity increase with increases in soil moisture. The SACOL observed soil moisture are also used to validate the AMSR-E/AQUA retrieved soil moisture and there is good agreement between them. The analysis of the relationship between satellite retrieved soil moisture and precipitation suggests that the variability of soil moisture depends on the variation of precipitation over the Loess Plateau.
