Conceptually, the logical volume layer sits between the application and physical layers.

从概念上讲，逻辑卷层位于应用程序层和物理层之间。

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Because RPR is a layer 2 MAC-based technology, it can operate over multiple physical layers, including SONET.

由于RPR是第二层基于MAC的技术，所以它能在多个物理层上工作，包括SONET。

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The design of MAC protocol can be improved by extracting information in network and physical layers.

通过提取网络层和物理层中的一些信息，可以改进MAC(介质访问控制)层协议的设计。

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We had to pass through several layers of physical security to get in, and the company assured us that the data was well defended from the numerous cyber-attacks that the centre experiences every day.

BBC: How safe is life online?

"Advanced imaging technology enhances security by safely screening passengers for metallic and non-metallic threats including weapons, explosives and other objects concealed under layers of clothing without physical contact, " Soule said.

CNN: Body scanners not 'magic technology' against terror

What I also can say is that every passenger that passes security checkpoints is subject to many layers of security, as we all know, including a thorough physical screening at the checkpoint as well as other measures.

WHITEHOUSE: Press Briefing