理学 国际空间数据处理大会 释 International Symposium on Spatial Data Handling; SDH 国际空间数据处理大会 国际地理联合会地理信息科学委员会发起的国际会议系列，是地理信息科学领域最早和最有代表性的国际会议之一。
网络与数据通信 协议体系与组成结构 释文 synchronous digital hierarchy, SDH 同步数字体系
- unlinking
- unlit side
- unloaded
- unloaded Q factor
- unloaded Q-factor
- unloaded standby
- unloading
- unloading chamber
- unloading deformation in rockmass
- unloading for underwater vehicle
- unloading machine
- unloading wave
- unlock
- unlocking
- unlocking mark left by the original key
- unlubricated
- unlubricated friction
- Unlucky Uncle Lucky in Love
- unmagnetized
- unmagnetized plasma
- unmanned aerial vehicle
- unmanned aerial vehicle autonomous control
- unmanned aerial vehicle command and control system
- unmanned aerial vehicle communication
- unmanned aerial vehicle coordinated formation control