搜题请搜索小程序“爱下问搜题”
问题 单项选择题 案例分析题

500kV单回架空送电线路，4分裂相导线，导线分裂间距为450mm，三相导线水平排列，间距12m，导线直径为26.82mm。

线路的正序电抗为0.3Ω／km，正序电纳为4.5×10-6S／km，请计算线路的波阻抗Zc最接近下列哪项数值（）？

A.258.2Ω

B.66.7Ω

C.387.3Ω

D.377.8Ω

答案

参考答案：A

单项选择题

A typical application of this (71) is ADSL. It is emerging as the technology for home-and small-office Internet connectivity. It provides either 1.5 Mb/s～8 Mb/s from the network to the user and 64 Kb/s～512 Kb/s in the reverse direction depending on the distance, 12 000 or 18 000 feet.. The different speed for each direction gives it the (72) label. ADSL is designed to take advantage of the fact that video-on demand, telecommuting, and Internet access traffic are inherently asymmetrical. The user (73) a brief message up to the network and receives a ton of data coming back, either a movie or a piece of data download. Under such a scenario, low-speed traffic to the network is just fine. ADSL delivers high (74) where you need it and only uses a single copper pair. Through multiplexing, it also reserves (75) of the bandwidth for POTS.

A．sends

B．personates

C．receives

D．writes
查看答案
单项选择题

拔除上颌第一磨牙时需麻醉（）

A.上牙槽中神经、腭前神经

B.上牙槽后神经、腭前神经

C.上牙槽中神经、上牙槽后神经

D.上牙槽后神经、上牙槽中神经、鼻腭神经

E.上牙槽后神经、上牙槽中神经、腭前神经
查看答案