High Electromechanical Coupling Coefficient of Longitudinally Excited Shear Wave Resonator Based on Optimized Bragg Structure.

In this work, a longitudinally excited shear-wave resonator (YBAR) based on single-crystalline lithium tantalate (LiTaO3, LT) thin film is proposed. The YBAR has a 200 nm X-cut thin film and molybdenum electrode. A high effective electromechanical coupling coefficient (k2eff) of up to 19% for the suspension-type structure was obtained. Furthermore, a Bragg reflector (SiO2/Pt) with optimized layer thickness ratio was employed to improve the performance of the YBAR. Compared to the acoustic wave resonators with the conventional quarter-wave (λ/4) Bragg reflector, the proposed YBAR with an optimized Bragg reflector can reflect both the longitudinal and shear waves efficiently, and resonators with spurious-free response and high quality (Q) value were achieved. This work provides a potential solution to enabling high coupling micro-acoustic resonators with high Q factor in the 5G/6G communication system.

Simulation on Heat Transfer and Emergency Protection of Tanks in a Tank Farm under Fire Scenario.

It is very important to understand the heat transfer process between storage tanks in a tank farm under a fire scenario, which is one of the key factors in determining the consequences of accident development. In this paper, a CFD simulation is used to study the heat transfer process and emergency protection of tanks under a fire scenario. The simulated results show that the changes in wind speed can affect the heat transfer of the tank farm. The highest temperature of the tanks at 5.3 m/s (wind speed) is 1432 K, while the highest temperature at 17.1 m/s (wind speed) is 1556 K. At the same time, the changes in wind direction can also affect the heat transfer of the tank farm. For the 45° east by north (wind direction), almost all tanks in the tank farm are affected by the fire. When the water curtain was applied as an emergency protection measure, the simulated highest temperature of the tanks decreased to 779 K (the cooling water intensity 6 L/min·m2), while the highest temperature of the tanks was 1432 K without water curtain protection under the actual fire conditions. The simulated highest temperature of the tanks decreased to 671 K when the emergency thermal insulation coating was sprayed on the surface of the tanks, which can effectively protect the adjacent tanks from being destroyed.