针对复杂输电环境下机械臂多目标点路径规划效率低、路径代价高的问题,提出了基于改进的人工势场引导的知情快速扩展随机树算法(improved artificial potential field-informed rapidly-exploring random trees star,IAPF-IRRT^(*))来...针对复杂输电环境下机械臂多目标点路径规划效率低、路径代价高的问题,提出了基于改进的人工势场引导的知情快速扩展随机树算法(improved artificial potential field-informed rapidly-exploring random trees star,IAPF-IRRT^(*))来提升路径规划的性能。首先引入长方体斥力场模型改进传统人工势场中球形斥力场模型,建立输电环境下复杂障碍物的斥力场。然后采用位置均匀分布的椭球域改进IAPF-IRRT*算法中的椭圆域,避免复杂输电环境下采样点出现局部冗余,提高搜索效率。最后引入三角寻优法优化路径中的冗余节点并结合三次样条插曲线对路径平滑处理。在三维简单、三维复杂和复杂输电环境这三组不同复杂程度的障碍物地图上进行验证,其结果表明:IAPF-IRRT*算法与标准RRT、RRT*算法相比,时间效率分别提升了44.8%~83.8%、68.3%~95.2%、26.5%~71.8%;路径代价分别降低了15.5%~35.0%、14.1%~35.3%、31.5%~43.5%;路径中的节点数量分别减少了75.6%~78.8%、75.0%~78.0%、70.4%~72.0%。展开更多
Wireless sensor nodes have the advantage of being low-cost,easily deployed and of good mobility.If deployed in an underground mine with existing underground transmission systems a wireless sensor network can improve t...Wireless sensor nodes have the advantage of being low-cost,easily deployed and of good mobility.If deployed in an underground mine with existing underground transmission systems a wireless sensor network can improve the collection of information.To get good transmission performance for 2.4 GHz wireless sensor nodes at the working face we calculated the reflection properties of electromagnetic waves from a flat metal plate.Using the cascade impedance method(CIM),we studied transmission attenuation and compared the results to actual tests.The results show that the effective transmission distance of 2.4 GHz wireless sensor nodes meets the stipulations of the ZigBee protocol.展开更多
According to the special environment conditions and characteristics of high altitude in Northwest China, the study on key technologies of 750-kV transmission and substation projects has gained fruitful results which a...According to the special environment conditions and characteristics of high altitude in Northwest China, the study on key technologies of 750-kV transmission and substation projects has gained fruitful results which are imperative not only to the construction of 750-kV transmission demonstrative project first in China, but also has laid a solid foundation for future UHV transmission constructions.展开更多
The strength of the power frequency electric intensity and magnetic field of the 500-kV double circuit transmission lines was calculated by using the equivalent charge method and the Ampere's Law, and the environm...The strength of the power frequency electric intensity and magnetic field of the 500-kV double circuit transmission lines was calculated by using the equivalent charge method and the Ampere's Law, and the environmental impact factors of the fields were evaluated. By optimizing the phase sequence, the frequency electric intensity and magnetic field strength can be reduced. Within a distance of 25 m from the center of the transmission line, the power frequency electric intensity and magnetic field strength fall off sharply with the distance increase. Finally, the best phase sequence and the minimum ground clearance of the transmission lines were obtained to meet the requirements of the least impact on envionment.展开更多
We analyzed plasma perturbations occurring in the coexisting environment of powerful VLF transmitter emission, intense lightning strokes and strong seismic activity during pregnant period. The results suggest that ano...We analyzed plasma perturbations occurring in the coexisting environment of powerful VLF transmitter emission, intense lightning strokes and strong seismic activity during pregnant period. The results suggest that anomalous electron bursts with energy dispersion in the range of ~100–350 keV, forming the "wisp" signature, are due to cyclotron resonance of electrons with monochromatic waves from the powerful NWC VLF transmitters during nighttime. The intense broad band VLF emissions (up-going 0+ whistlers) are observed while the DEMETER satellite goes through the region of intense thunderstorm activities at mid-latitudes. However, the effects of intense lightning activity and pregnant earthquake have little impact on this kind of stable energy-dispersed electron structures, despite the fact that they are presumably two primary reasons for the particle precipitation in the ionosphere. The case studied here provides us a valuable opportunity to address the various sources triggering the anomalous plasma perturbations in the ionosphere.展开更多
文摘针对复杂输电环境下机械臂多目标点路径规划效率低、路径代价高的问题,提出了基于改进的人工势场引导的知情快速扩展随机树算法(improved artificial potential field-informed rapidly-exploring random trees star,IAPF-IRRT^(*))来提升路径规划的性能。首先引入长方体斥力场模型改进传统人工势场中球形斥力场模型,建立输电环境下复杂障碍物的斥力场。然后采用位置均匀分布的椭球域改进IAPF-IRRT*算法中的椭圆域,避免复杂输电环境下采样点出现局部冗余,提高搜索效率。最后引入三角寻优法优化路径中的冗余节点并结合三次样条插曲线对路径平滑处理。在三维简单、三维复杂和复杂输电环境这三组不同复杂程度的障碍物地图上进行验证,其结果表明:IAPF-IRRT*算法与标准RRT、RRT*算法相比,时间效率分别提升了44.8%~83.8%、68.3%~95.2%、26.5%~71.8%;路径代价分别降低了15.5%~35.0%、14.1%~35.3%、31.5%~43.5%;路径中的节点数量分别减少了75.6%~78.8%、75.0%~78.0%、70.4%~72.0%。
基金Project 60774090 supported by the National Natural Science Foundation of China
文摘Wireless sensor nodes have the advantage of being low-cost,easily deployed and of good mobility.If deployed in an underground mine with existing underground transmission systems a wireless sensor network can improve the collection of information.To get good transmission performance for 2.4 GHz wireless sensor nodes at the working face we calculated the reflection properties of electromagnetic waves from a flat metal plate.Using the cascade impedance method(CIM),we studied transmission attenuation and compared the results to actual tests.The results show that the effective transmission distance of 2.4 GHz wireless sensor nodes meets the stipulations of the ZigBee protocol.
文摘According to the special environment conditions and characteristics of high altitude in Northwest China, the study on key technologies of 750-kV transmission and substation projects has gained fruitful results which are imperative not only to the construction of 750-kV transmission demonstrative project first in China, but also has laid a solid foundation for future UHV transmission constructions.
文摘The strength of the power frequency electric intensity and magnetic field of the 500-kV double circuit transmission lines was calculated by using the equivalent charge method and the Ampere's Law, and the environmental impact factors of the fields were evaluated. By optimizing the phase sequence, the frequency electric intensity and magnetic field strength can be reduced. Within a distance of 25 m from the center of the transmission line, the power frequency electric intensity and magnetic field strength fall off sharply with the distance increase. Finally, the best phase sequence and the minimum ground clearance of the transmission lines were obtained to meet the requirements of the least impact on envionment.
基金supported by the National Natural Science Foundation of China (Grant No. 41431071)
文摘We analyzed plasma perturbations occurring in the coexisting environment of powerful VLF transmitter emission, intense lightning strokes and strong seismic activity during pregnant period. The results suggest that anomalous electron bursts with energy dispersion in the range of ~100–350 keV, forming the "wisp" signature, are due to cyclotron resonance of electrons with monochromatic waves from the powerful NWC VLF transmitters during nighttime. The intense broad band VLF emissions (up-going 0+ whistlers) are observed while the DEMETER satellite goes through the region of intense thunderstorm activities at mid-latitudes. However, the effects of intense lightning activity and pregnant earthquake have little impact on this kind of stable energy-dispersed electron structures, despite the fact that they are presumably two primary reasons for the particle precipitation in the ionosphere. The case studied here provides us a valuable opportunity to address the various sources triggering the anomalous plasma perturbations in the ionosphere.
