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A smart base-isolation system, composed of low damping bearings and piezoelectric friction damper is studied in this paper. The semi-active piezoelectric friction damper (PFD[1]) is proposed for control of peak dynamic response of seismic-excited structures. In the proposed PFD device, the friction force between two sliding plates is regulated by controlling the normal force using piezoelectricity across the damper, and its advantage is that its operation requires only minimal external power. A high efficient control algorithm is proposed for the semi-active control of the friction damper using a simple static output. The effectiveness of the PFD device and the control strategy in reducing the peak dynamic response of structures is investigated through an application to a 5-story base-isolated building. Numerical results demonstrate that the proposed PFD device and the control strategy are effective in reducing the peak drift of rubber-bearings of the base-isolated building subject to earthquakes.

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Redundancy is generally considered in the computer room air conditioners (CRACs) of the data center room. The position of the CRAC in the on state and the operating air volume have a great influence on the temperature distribution. The temperature distribution of the data center room will affect the failure rate of the servers and the energy consumption of the air-conditioning system. Taking a typical data center room as an example, this paper uses numerical simulation to study the influence of the on/off state and air volume of CRACs on the temperature distribution of the hot and cold aisles and energy consumption. The calculation results show that we should preferably turn off the staggered CRACs on the opposite side and close to the middle position under the partial load. When the IT load is unevenly distributed, it is irrational to use the setting method of even distribution of the air volume of each CRAC. The air volume of each CRAC should be appropriately adjusted based on the distribution characteristic of IT load to reduce the energy consumption.