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The performance of gas blown in side walls of a single strand tundish is numerically simulated. Three cases are studied, i.e. tundish without gas blown, tundish with gas blown from the right side wall, and from the front wall. The vortex circulating flow is the main flow structure in tundish without gas blown. The gas blown from the right side wall of tundish will significantly change the flow field. The short-circuit flow that the tracer flow along the bottom of tundish to the outlet is becoming the main flow pattern. The RTD curve shows a rapid increase tendency. An anticlockwise flow near the top surface is formed. The mixing of tracer in the tundish is delayed and the dead volume fraction is increased when compared with the tundish without gas blown case. In contrast, the gas blown from the front wall of tundish will divide the tundish into two parts. The strong circulation flow in two parts is formed. Besides, the mixing of tracer is faster and the dead volume fraction is lower than that of the case without gas blown. This case may be an optimized gas blown technology in tundish.

Electrochemical CO2 reduction reaction (CO2RR) is the key part of clean energy generation and utilization, which has great potential to help the world to reach the carbon-neutral energy cycle in the future. In line with the development of metal-organic frameworks (MOFs) with the large specific area and considerable porosity in the past two decades, some of the MOF-based electrocatalysts have shown superior ability to accelerate CO2RR. However, regarding such a significant CO2RR process, some critical disadvantages, including inferior robustness, low yield and selectivity, and idealistic working environment, are still required to be concentrated on. Herein, a comprehensive outline of the reaction mechanism of CO2 conversion and rational synthesis of the state-of-the-art pristine MOFs is given. Further, recent progress of pristine MOF-based electrocatalysts in CO2RR is systematically summarized. Lastly, the major limitations and future opportunities in MOF electrocatalysis for CO2RR are presented.

In this paper, we have studied the effect of air pressure damping on the vibration- based energy harvesting devices. The device we used is an electrostatic energy harvester with an out-of-the-plane gap closing scheme. A broadened bandwidth is observed at 4 Pa when the acceleration is increased from 0.5 m/s2. A power output of 2.2 μW is achieved at the air pressure of 4 Pa when a low acceleration of 0.5 m/s2 is applied, while the power output is only 0.02 μW at atmosphere with an acceleration of 1.2 m/s2. Detailed study is made to investigate the waveform of the displacement and the voltage output. Nonlinearity is observed at low air gas pressure about 239 Pa and it is more significant at 4 Pa.

Order tracking is one of the most effective algorithms to eliminate the effect of time-varying rotational speed on the rotary machines. However, this algorithm is not suitable for the faulty rolling bearing unless the peak time of the fault-induced impulse is set as zero which cannot be met in the real engineering. The traditional resampling process will cause uneven intervals between the adjacent impulse peaks in the angular domain and then affect the envelope analysis-based diagnosis result. To solve this problem, a new resampling algorithm with three parts is proposed: (a) linearly fitting the instantaneous rotational speed measured by the tachometer, (b) resampling the vibration signal from the time domain to the angular domain using the traditional method, (c) calculating the envelope deformation amount and then compensating the resampled result. The effectiveness of the proposed method has been validated by both the simulated and experimental bearing vibration signals.