Abstract: A method for preparing low-background cement includes: uniformly mixing a seed crystal of cement, C4AF whiskers, and high-magnesium raw material to yield a first mixture, calcining the first mixture at 1400-1500° C., to yield a low-background clinker, the first mixture including 1.0-5.0 wt. % of the seed crystal of cement, 1.0-5.0 wt. % of the C4AF whiskers, and the balance is the high-magnesium raw material; and grinding a second mixture of the low-background clinker and gypsum, to yield low-background cement. The seed crystal of cement is a high-magnesium and low hydration heat clinker, has a specific activity of Ra-226 radioactive nuclides within 50 Bq/kg, and the MgO content of the clinker is between 4.0 wt. % and 5.0 wt. %, with 50 wt. % <C3S <55.0 wt. %; and the high-magnesium raw material has a MgO content between 2.5 wt. % and 3.0 wt. %.

Abstract: The present invention provides a method for recording programs, a multimedia system and a network side device. The multimedia system includes a network side device and a plurality of nodes, wherein the network side device is configured to generate a recording task after receiving a recording request, and send in advance the recording task to each node in which a channel specified in the recording task is stored, and the nodes are configured to record a program on the channel specified in the recording task after receiving the recording task, and return recording result information to the network side device. According to the recording method of the present invention, when the recording is failed, inter-node mutual reconstruction and complementary recording can be performed, which greatly decreases the possibility of failure in the recording of the program, and provides the quality of service of more fluent TVOD for users.

Abstract: The present invention provides a method for recording programs, a multimedia system and a network side device. The multimedia system includes a network side device and a plurality of nodes, wherein the network side device is configured to generate a recording task after receiving a recording request, and send in advance the recording task to each node in which a channel specified in the recording task is stored, and the nodes are configured to record a program on the channel specified in the recording task after receiving the recording task, and return recording result information to the network side device. According to the recording method of the present invention, when the recording is failed, inter-node mutual reconstruction and complementary recording can be performed, which greatly decreases the possibility of failure in the recording of the program, and provides the quality of service of more fluent TVOD for users.