排序方式: 共有64条查询结果,搜索用时 843 毫秒
1.
2.
3.
美国和欧盟高等级中心城市发展规律及其启示 总被引:2,自引:0,他引:2
对美国和欧盟的高等级中心城市的发展规律和经验开展了系统研究,发现美国和欧盟的高等级中心城市呈现显著的多中心分布格局,功能分工高度扁平化,面向全球、国际和国家各层级的城市体系完备等规律和特征。基于美国和欧盟经验,研究认为应从国家公共治理角度,对国家中心城市的政策内涵进行重新认识,突出国家中心城市的政策内涵和战略意图,将国家中心城市作为贯彻落实国家发展战略的重要平台和战略支点。应立足长远战略视野,循序渐进培育一大批扁平化功能分工的高等级国家中心城市,代表中国参与国际竞争、支撑国家整体长远发展。同时应深入明确和落实国家中心城市的战略职责和发展建设要求,确保国家战略意图、战略目标、战略任务得到有效贯彻和落实。 相似文献
5.
7.
基于现有的锂离子电池制造水平,单体电池存在一定差异,为了避免个别单体的过充、过放所导致的电池组失效,使其性能接近单体电池的平均水平。应对电池组中各单体之间实现均衡控制。描述了电池的均衡控制方法、电路设计和实现步骤,并对锂离子电池进行均衡充电试验。结果表明该方法能有效的弥补电池的不一致性。 相似文献
8.
The microstructure and tensile properties of Sn-9Zn solder under different cooling and aging condition were studied.During solidification, the distribution of Zn-rich phases and grain size in the microstructure of Sn-9Zn solder were decided by the cooling rate.The Zn-rich phase in Sn-9Zn solder under furnace cooling, air cooling and water cooling media was separately existed as coarsen dendritic and needle like shape, fine needle like shape and very fine rod-like shape, respectively.After aging, the coarsen dendritic was broken and the coarsen needle like Zn-rich phase was partly changed into fine distribution of Zn-rich phase for Sn-9Zn solder with furnace cooling, and the rod-like Zn phase in the Sn-9Zn solder under water cooling was changed to conglomerated Zn with needle shape.During tensile testing on Sn-9Zn solder, tensile strength and ductility reached the best with water cooling, but decreased with aging effect.Meanwhile, the ductility of solder with air cooling and the strength of solder with furnace cooling increased with aging.The fracture mode was ductile and was independent of cooling media and aging effect.The size and depth of dimples decreased from water, furnace to air cooling.After aging, number and size of dimples increased on the solder with furnace cooling and air cooling.The change on the size of dimples for the Sn-9Zn solder under different cooling condition and with aging effect was accordance to the tensile properties. 相似文献
9.
输煤系统具有现场环境粉尘浓度高,控制电缆用量大,电缆通道复杂,施工工作量大,工程建设一次性投资费用高等特点。该文在实际工程中,根据输煤控制的特点实现总线控制,结合Profibus总线中智能马达保护器可提供大量诊断信息;根据相关故障诊断信息,建立设备健康优先级启动顺序,并通过设备健康优先级管理实现从煤源到煤仓间一键启停控制;再结合诊断信息的保护动作信息,确保处于故障中设备的保护跳闸动作准确,优化设备启停时间,降低设备损耗,确保设备最优运行效率,从而提升输煤控制水平。 相似文献
10.