The optimal design method for an open Magnetic Resonance Imaging （MRI） superconducting magnet with an active shielding configuration is proposed. Firstly, three pairs of current rings are employed as seed coils. By ...The optimal design method for an open Magnetic Resonance Imaging （MRI） superconducting magnet with an active shielding configuration is proposed. Firstly, three pairs of current rings are employed as seed coils. By optimizing the homogeneity of Diameter Sphere Voltnne （DSV）, the positions and currents of the seed coils will be obtained. Secondly, according to the positions and currents of the seed coils, the current density of superconducting wires is determined, and then the original sections for the coils can be achieved. An optimization for the homogeneity based on the constrained nonlincar optimization method is employed to determine the coils with good homogeneity. Thirdly, the magnetic field generated by previous coils is set as the background field, then add two coils with reverse current, and optimize the stray field line of 5 Gauss in a certain scope. Finally, a further optimization for the homogeneity is used to get Final coils. This method can also be used in the design of other axisynmaetfic superconducting MRI magnets.展开更多
English thesis writing and tutoring process is traditionally loose and open-ended. Both students and teachers enjoy much liberty in the maneuver of different steps in the whole process, which, as it were, may cause a ...English thesis writing and tutoring process is traditionally loose and open-ended. Both students and teachers enjoy much liberty in the maneuver of different steps in the whole process, which, as it were, may cause a series of problems and dissatisfactions, consequently undermining the quality and significance. This paper is intended to explore a streamlined and systematic procedure to ensure both the students and teachers are doing their bit and make due contribution to the thesis perfection.展开更多
This paper presents an ANN （artificial neural networks）-based technique for improving the performance of distance relays against open-circuit faults in transmission networks. The technique utilizes the small capacit...This paper presents an ANN （artificial neural networks）-based technique for improving the performance of distance relays against open-circuit faults in transmission networks. The technique utilizes the small capacitive current measured in the open-phase plus the currents in the two healthy phases in calculating the open-circuit fault distance. The results obtained show that a distance relay with the proposed scheme will not only be able to detect the open-conductor condition in HVTL （high voltage transmission line） but also to locate the place of this fault regardless the value of the pre-fault current loading. There is no need for especial communication schemes since the existing media could work properly for the needs of the proposed technique.展开更多
The new approaches to construct deep blue aggregation-induced emission （ALE） materials have been explored, which control the conjugation by two different strategies, to make a great step for the commercialization of...The new approaches to construct deep blue aggregation-induced emission （ALE） materials have been explored, which control the conjugation by two different strategies, to make a great step for the commercialization of organic light-emitting diodes. In order to shorten the intramolecular conjugation length, triphenylethylene （tPE） was utilized to construct blue AIEgens as peripheral groups, instead of tetraphenylethylene （TPE）, the famous AIE star molecule, to yield three blue AIEgens of 3,4-BtPE-PI, 4,4- BtPE-PI and 4,4-BtPE-PPI. Nondoped electroluminescence devices are fabricated by using these three AIEgens as the emitting material layer, the best performance of 3.8 cd/A as the maximum current efficiency achieved at the commission internationale de l＇Eclairage coordinates of （0.17, 0.18）.展开更多
The spontaneous emission(SE) of Er3+ embedded in a double slot dielectric structure was studied by a quantum-electrodynamical formalism. The study shows that the slot width and the position of Er3+ in slot structure h...The spontaneous emission(SE) of Er3+ embedded in a double slot dielectric structure was studied by a quantum-electrodynamical formalism. The study shows that the slot width and the position of Er3+ in slot structure have a significant effect on the SE. The double slot waveguides were fabricated by embedding two low-index Er/Yb silicate material layers into high-index silicon. The radiative efficiency of Er3+ in the double slot waveguides is found to be higher than that of the single slot waveguide, which is consistent with the theory simulation. The 0.67 d B signal enhancement at 1.53 ?m in a 4.6-mm-long slot waveguide was observed pumped by 1476 nm laser. These results show the relevance of our model to study the SE processes in multilayer structures and are important for future realization of silicon-compatible active optical devices.展开更多
基金supported by the National Natural Science Foundation of China(No.50577063)
文摘The optimal design method for an open Magnetic Resonance Imaging （MRI） superconducting magnet with an active shielding configuration is proposed. Firstly, three pairs of current rings are employed as seed coils. By optimizing the homogeneity of Diameter Sphere Voltnne （DSV）, the positions and currents of the seed coils will be obtained. Secondly, according to the positions and currents of the seed coils, the current density of superconducting wires is determined, and then the original sections for the coils can be achieved. An optimization for the homogeneity based on the constrained nonlincar optimization method is employed to determine the coils with good homogeneity. Thirdly, the magnetic field generated by previous coils is set as the background field, then add two coils with reverse current, and optimize the stray field line of 5 Gauss in a certain scope. Finally, a further optimization for the homogeneity is used to get Final coils. This method can also be used in the design of other axisynmaetfic superconducting MRI magnets.
文摘English thesis writing and tutoring process is traditionally loose and open-ended. Both students and teachers enjoy much liberty in the maneuver of different steps in the whole process, which, as it were, may cause a series of problems and dissatisfactions, consequently undermining the quality and significance. This paper is intended to explore a streamlined and systematic procedure to ensure both the students and teachers are doing their bit and make due contribution to the thesis perfection.
文摘This paper presents an ANN （artificial neural networks）-based technique for improving the performance of distance relays against open-circuit faults in transmission networks. The technique utilizes the small capacitive current measured in the open-phase plus the currents in the two healthy phases in calculating the open-circuit fault distance. The results obtained show that a distance relay with the proposed scheme will not only be able to detect the open-conductor condition in HVTL （high voltage transmission line） but also to locate the place of this fault regardless the value of the pre-fault current loading. There is no need for especial communication schemes since the existing media could work properly for the needs of the proposed technique.
基金supported by the National Natural Science Foundation of China (21325416 and 51573140)the National Basic Research Program of China (2013CB834701)
文摘The new approaches to construct deep blue aggregation-induced emission （ALE） materials have been explored, which control the conjugation by two different strategies, to make a great step for the commercialization of organic light-emitting diodes. In order to shorten the intramolecular conjugation length, triphenylethylene （tPE） was utilized to construct blue AIEgens as peripheral groups, instead of tetraphenylethylene （TPE）, the famous AIE star molecule, to yield three blue AIEgens of 3,4-BtPE-PI, 4,4- BtPE-PI and 4,4-BtPE-PPI. Nondoped electroluminescence devices are fabricated by using these three AIEgens as the emitting material layer, the best performance of 3.8 cd/A as the maximum current efficiency achieved at the commission internationale de l＇Eclairage coordinates of （0.17, 0.18）.
基金supported by the National Natural Science Foundation of China(Grant Nos.61377056 and 61320106001)the Program for New Century Excellent Talents in University
文摘The spontaneous emission(SE) of Er3+ embedded in a double slot dielectric structure was studied by a quantum-electrodynamical formalism. The study shows that the slot width and the position of Er3+ in slot structure have a significant effect on the SE. The double slot waveguides were fabricated by embedding two low-index Er/Yb silicate material layers into high-index silicon. The radiative efficiency of Er3+ in the double slot waveguides is found to be higher than that of the single slot waveguide, which is consistent with the theory simulation. The 0.67 d B signal enhancement at 1.53 ?m in a 4.6-mm-long slot waveguide was observed pumped by 1476 nm laser. These results show the relevance of our model to study the SE processes in multilayer structures and are important for future realization of silicon-compatible active optical devices.
