Theoretical insights elucidate a series of active phosphonate esters application in preparation of Cephalosporin antibiotics’ intermediate. The B3LYP/6-311+G(d,p) method was employed to obtain the stable equilibrium ...Theoretical insights elucidate a series of active phosphonate esters application in preparation of Cephalosporin antibiotics’ intermediate. The B3LYP/6-311+G(d,p) method was employed to obtain the stable equilibrium geometries including comparing to the AE-active ester. It was found that the Ethyl-aminothiazoly Loximate (AT) molecule fragment is almost planar sheet, but it is almost perpendicular to the plane of phosphoryl ester. Moreover, the calculated Mulliken atomic charge distribution and frontier molecular orbital analysis of these esters showed that the amino N atom connected to the Thiazole ring of the AT had the maximum negative charge, which suggested that this area had high molecular activity. The value of ΔEL-H was energy gap between EHOMO and ELUMO and indicated that compound 6a had high reaction activity. The theory calculation results can explain the reaction mechanism well and predict that the novel active phosphonate ester has a hopeful application prospect in preparation of Cephalosporin antibiotics’ intermediate.展开更多
The gradient doping regions were employed in the emitter layer and the base layer of GaAs based laser power converters(LPCs).Silvaco TCAD was used to numerically simulate the linear gradient doping and exponential gra...The gradient doping regions were employed in the emitter layer and the base layer of GaAs based laser power converters(LPCs).Silvaco TCAD was used to numerically simulate the linear gradient doping and exponential gradient doping structure,and analyze the transport process of photogenerated carriers.Energy band adjustment via gradient doping improved the separation and transport efficiency of photogenerated carriers and reduced the total recombination rate of GaAs LPCs.Compared with traditional structure of LPCs,the photoelectric conversion efficiency of LPCs with linear and exponential gradient doping structure were improved from 52.7%to 57.2%and 57.7%,respectively,under 808 nm laser light at the power density of 1 W/cm^(2).展开更多
A hot spot is a reliability problem in photovoltaic(PV) modules where a mismatched or shaded cell heats up significantly and degrades the PV module output power performance. High PV cell temperature due to a hot spot ...A hot spot is a reliability problem in photovoltaic(PV) modules where a mismatched or shaded cell heats up significantly and degrades the PV module output power performance. High PV cell temperature due to a hot spot can damage the cell encapsulate and lead to second breakdown, which both cause permanent damage to the PV module. In present systems, bypass diodes are used to mitigate the hot spot problem. In this work, five commercial polysilicon P V modules configured with different numbers of bypass diodes are used to study the influence of bypass diodes on the reverse bias voltage of a shaded cell and the resulting hot spot phenomenon. The reverse bias voltage of the shaded cell, and the hot spot probability and severity decrease as the number of bypass diodes increases. Negative terminal voltage of a shaded cell accompanied by a switched-off bypass diode are the necessary condition for hot spot generation. In an extreme case where each cell has an individual bypass diode in a P V module, it still cannot avoid the hazards of a hot spot under the shading areas of 5-7 cm2, but the probability of a hot spot is reduced to a minimum of 0.41%.展开更多
文摘Theoretical insights elucidate a series of active phosphonate esters application in preparation of Cephalosporin antibiotics’ intermediate. The B3LYP/6-311+G(d,p) method was employed to obtain the stable equilibrium geometries including comparing to the AE-active ester. It was found that the Ethyl-aminothiazoly Loximate (AT) molecule fragment is almost planar sheet, but it is almost perpendicular to the plane of phosphoryl ester. Moreover, the calculated Mulliken atomic charge distribution and frontier molecular orbital analysis of these esters showed that the amino N atom connected to the Thiazole ring of the AT had the maximum negative charge, which suggested that this area had high molecular activity. The value of ΔEL-H was energy gap between EHOMO and ELUMO and indicated that compound 6a had high reaction activity. The theory calculation results can explain the reaction mechanism well and predict that the novel active phosphonate ester has a hopeful application prospect in preparation of Cephalosporin antibiotics’ intermediate.
基金This work was supported by the National Key R&D Program of China(No.2018YFB1500500)also supported by Ally Fund of Chinese Academy of Sciences(No.Y072051002).
文摘The gradient doping regions were employed in the emitter layer and the base layer of GaAs based laser power converters(LPCs).Silvaco TCAD was used to numerically simulate the linear gradient doping and exponential gradient doping structure,and analyze the transport process of photogenerated carriers.Energy band adjustment via gradient doping improved the separation and transport efficiency of photogenerated carriers and reduced the total recombination rate of GaAs LPCs.Compared with traditional structure of LPCs,the photoelectric conversion efficiency of LPCs with linear and exponential gradient doping structure were improved from 52.7%to 57.2%and 57.7%,respectively,under 808 nm laser light at the power density of 1 W/cm^(2).
基金Project supported by the National Natural Science Foundation of China(No.61504139,61275040)Chinese Academy of Sciences(No.Y072051002)
文摘A hot spot is a reliability problem in photovoltaic(PV) modules where a mismatched or shaded cell heats up significantly and degrades the PV module output power performance. High PV cell temperature due to a hot spot can damage the cell encapsulate and lead to second breakdown, which both cause permanent damage to the PV module. In present systems, bypass diodes are used to mitigate the hot spot problem. In this work, five commercial polysilicon P V modules configured with different numbers of bypass diodes are used to study the influence of bypass diodes on the reverse bias voltage of a shaded cell and the resulting hot spot phenomenon. The reverse bias voltage of the shaded cell, and the hot spot probability and severity decrease as the number of bypass diodes increases. Negative terminal voltage of a shaded cell accompanied by a switched-off bypass diode are the necessary condition for hot spot generation. In an extreme case where each cell has an individual bypass diode in a P V module, it still cannot avoid the hazards of a hot spot under the shading areas of 5-7 cm2, but the probability of a hot spot is reduced to a minimum of 0.41%.