在永磁电机设计中,永磁体(permanent magnet,PM)作为励磁磁源,其结构、尺寸直接影响电机的性能。进化策略(evolution strategies,ES)是一类仿效自然选择和基因突变的智能优化算法,具有适应性广、鲁棒性好、适用于并行计算等优点。该文...在永磁电机设计中,永磁体(permanent magnet,PM)作为励磁磁源,其结构、尺寸直接影响电机的性能。进化策略(evolution strategies,ES)是一类仿效自然选择和基因突变的智能优化算法,具有适应性广、鲁棒性好、适用于并行计算等优点。该文将ES引进到永磁电机PM结构的优化设计中,并将有限元分析(finite element analysis,FEA)与ES相结合进行优化设计。以一台8.5 k W的轮毂电机作为优化对象,通过联合ES和FEA对PM结构尺寸进行优化,轮毂电机的齿槽转矩有效减小了81.7%,平均电磁转矩增大了5.3%。展开更多
Permanent magnetic materials capable of operating at high temperature up to 500℃ have wide potential applications in fields such as aeronautics, space, and electronic cars. SmCo alloys are candidates for high tempera...Permanent magnetic materials capable of operating at high temperature up to 500℃ have wide potential applications in fields such as aeronautics, space, and electronic cars. SmCo alloys are candidates for high temperature applications, since they have large magnetocrystalline anisotropy field （6-30 T）, high Curie temperature （720-920℃）, and large energy product （〉200 kJ.m-3） at room temperature. However, the highest service temperature of commercial 2：17 type SmCo magnets is only 300℃, and many efforts have been devoted to develop novel high temperature permanent magnets. This review focuses on the development of three kinds of SmCo based magnets： 2：17 type SmCo magnets, nanocrystalline SmCo magnets, and nanocomposite SmCo magnets. The oxidation protection, including alloying and surface modification, of high temperature permanent magnets is discussed as well.展开更多
The polypropylene for preparing packing(biofilm carrier) used in biodegradation of wastewater was modified by adding some biocompatible, hydrophilic and magnetic additives such as stearic acid, polyvinyl alcohol, acti...The polypropylene for preparing packing(biofilm carrier) used in biodegradation of wastewater was modified by adding some biocompatible, hydrophilic and magnetic additives such as stearic acid, polyvinyl alcohol, activated carbon and magnetic powders.The prepared packing was then magnetized in a magnetizer to be charged with a 2.5×10 -3 —5.0×10 -3 tesla permanent magnet.The wettablity and biofilm formation performance of the modified and magnetized packing were tested.The result showed that the adsorbed water content of the polypropylene packing increased more than 300% and the period of biofilm formation reduced from 7—9 days to within 2 days after modification and magnetization.The removal rate of COD Cr by the modified and magnetized packing was also proved to be 30% higher than that by the original polypropylene packing.展开更多
Tuned mass dampers （TMDs） have been widely used in recent years to mitigate structural vibration. However, the damping mechanisms employed in the TMDs are mostly based on viscous dampers, which have several well-kno...Tuned mass dampers （TMDs） have been widely used in recent years to mitigate structural vibration. However, the damping mechanisms employed in the TMDs are mostly based on viscous dampers, which have several well-known disadvantages, such as oil leakage and difficult adjustment of damping ratio for an operating TMD. Alternatively, eddy current damping （ECD） that does not require any contact with the main structure is a potential solution. This paper discusses the design, analysis, manufacture and testing of a large-scale horizontal TMD based on ECD. First, the theoretical model of ECD is formulated, then one large-scale horizontal TMD using ECD is constructed, and finally performance tests of the TMD are conducted. The test results show that the proposed TMD has a very low intrinsic damping ratio, while the damping ratio due to ECD is the dominant damping source, which can be as large as 15% in a proper configuration. In addition, the damping ratios estimated with the theoretical model are roughly consistent with those identified from the test results, and the source of this error is investigated. Moreover, it is demonstrated that the damping ratio in the proposed TMD can be easily adjusted by varying the air gap between permanent magnets and conductive plates. In view of practical applications, possible improvements and feasibility considerations for the proposed TMD are then discussed. It is confirmed that the proposed TMD with ECD is reliable and feasible for use in structural vibration control.展开更多
文摘在永磁电机设计中,永磁体(permanent magnet,PM)作为励磁磁源,其结构、尺寸直接影响电机的性能。进化策略(evolution strategies,ES)是一类仿效自然选择和基因突变的智能优化算法,具有适应性广、鲁棒性好、适用于并行计算等优点。该文将ES引进到永磁电机PM结构的优化设计中,并将有限元分析(finite element analysis,FEA)与ES相结合进行优化设计。以一台8.5 k W的轮毂电机作为优化对象,通过联合ES和FEA对PM结构尺寸进行优化,轮毂电机的齿槽转矩有效减小了81.7%,平均电磁转矩增大了5.3%。
基金supported by the National Natural Science Foundation of China (Nos. 51071010 and 50925101)the Innovation Foundation of Beihang University for Ph.D. Graduates
文摘Permanent magnetic materials capable of operating at high temperature up to 500℃ have wide potential applications in fields such as aeronautics, space, and electronic cars. SmCo alloys are candidates for high temperature applications, since they have large magnetocrystalline anisotropy field （6-30 T）, high Curie temperature （720-920℃）, and large energy product （〉200 kJ.m-3） at room temperature. However, the highest service temperature of commercial 2：17 type SmCo magnets is only 300℃, and many efforts have been devoted to develop novel high temperature permanent magnets. This review focuses on the development of three kinds of SmCo based magnets： 2：17 type SmCo magnets, nanocrystalline SmCo magnets, and nanocomposite SmCo magnets. The oxidation protection, including alloying and surface modification, of high temperature permanent magnets is discussed as well.
基金广东省自然科学基金 (No 0 115 63 )广东省科技计划项目 (No 2 0 0 2C3 163 1)国家环保局华南环境科学研究所青年基金资助项目~~
文摘The polypropylene for preparing packing(biofilm carrier) used in biodegradation of wastewater was modified by adding some biocompatible, hydrophilic and magnetic additives such as stearic acid, polyvinyl alcohol, activated carbon and magnetic powders.The prepared packing was then magnetized in a magnetizer to be charged with a 2.5×10 -3 —5.0×10 -3 tesla permanent magnet.The wettablity and biofilm formation performance of the modified and magnetized packing were tested.The result showed that the adsorbed water content of the polypropylene packing increased more than 300% and the period of biofilm formation reduced from 7—9 days to within 2 days after modification and magnetization.The removal rate of COD Cr by the modified and magnetized packing was also proved to be 30% higher than that by the original polypropylene packing.
基金State Key Program of Natural Science Foundation of China Under Grant No.50738002
文摘Tuned mass dampers （TMDs） have been widely used in recent years to mitigate structural vibration. However, the damping mechanisms employed in the TMDs are mostly based on viscous dampers, which have several well-known disadvantages, such as oil leakage and difficult adjustment of damping ratio for an operating TMD. Alternatively, eddy current damping （ECD） that does not require any contact with the main structure is a potential solution. This paper discusses the design, analysis, manufacture and testing of a large-scale horizontal TMD based on ECD. First, the theoretical model of ECD is formulated, then one large-scale horizontal TMD using ECD is constructed, and finally performance tests of the TMD are conducted. The test results show that the proposed TMD has a very low intrinsic damping ratio, while the damping ratio due to ECD is the dominant damping source, which can be as large as 15% in a proper configuration. In addition, the damping ratios estimated with the theoretical model are roughly consistent with those identified from the test results, and the source of this error is investigated. Moreover, it is demonstrated that the damping ratio in the proposed TMD can be easily adjusted by varying the air gap between permanent magnets and conductive plates. In view of practical applications, possible improvements and feasibility considerations for the proposed TMD are then discussed. It is confirmed that the proposed TMD with ECD is reliable and feasible for use in structural vibration control.
