Atmospheric Anomaly Analysis Related to Ms > 6.0 Earthquakes in China during 2020–2021

The attention towards links of atmospheric parameter variation and earthquakes has increased exponentially by utilizing new methods and more accurate observations. Persistent research makes it possible to gain insight into the precursor mechanism of earthquakes. In this paper, we studied the universality of detecting atmospheric anomalies associated with earthquakes based on tidal force fluctuation in China for earthquakes of Ms > 6.0, and explored the influence of tidal force on tectonic stress. The data of air temperature, geopotential height, ozone mixing ratio, and relative humidity from the National Center for Environmental Prediction (NCEP) were analyzed to reveal the spatiotemporal variation of atmospheric anomalies at multiple isobaric surfaces. Furthermore, the coupling of atmospheric parameters was investigated. The results showed that continuous solicitation exerted by tidal forces could change the strength of tectonic stress that causes earthquakes. The evolution pattern of air temperature, geopotential height, and relative humidity could be supported by atmospheric thermal vertical diffusion, while the anomalies of ozone mixing ratio was not evident. This verified the feasibility of detecting multi-parameter atmospheric anomalies associated with earthquakes based on tidal force fluctuation. Our results provide more evidence for understanding the atmospheric precursor characteristics of earthquakes.

Modeling and suppression of unbalanced radial force for in-wheel motor driving system

Considering the negative vertical dynamics effect of switched reluctance motor on an in-wheel motor driving system, this article presents a modeling and suppression method for unbalanced radial force of the in-wheel motor driving system. To tease out the coupling relationship within the in-wheel motor driving system, this investigation, respectively, explores the principle of unbalanced radial force and the coupling relationship between rotor eccentricity and road excitation based on the suspension response model with unbalanced radial force under road excitation. The switched reluctance motor nonlinear analytical model was fitted by the Fourier series, and its radial electromagnetic force was modeled and analyzed by the Maxwell stress tensor method. To mitigate the influence of radial electromagnetic force fluctuation and unbalanced radial force amplitude value under eccentricity condition on the in-wheel motor driving system, the elitist non-dominated sorting genetic algorithm was adopted to improve radial electromagnetic force fluctuation and unbalanced radial force amplitude value of the switched reluctance motor. The simulation results show that the proposed optimization method can suppress the radial electromagnetic force fluctuation and unbalanced radial force amplitude value, and the negative effect of vertical dynamics of the in-wheel motor driving system is conspicuously mitigated.

Uniformity, Periodicity and Symmetry Characteristics of Forces Fluctuation in Helical-Edge Milling Cutter

Under most processing conditions, the milling force is expected to be stable and not to fluctuate, in order to improve the processing quality. This study focuses on analyzing the force fluctuation characteristics under conditions of different processing and cutter parameters. An original model is proposed to predict the force fluctuation during the milling process of a helical-edge cutter. At the same time, three force fluctuation characteristics related to the axial cutting depth and cutter parameters are determined: uniformity, periodicity and symmetry. The corresponding mathematical derivation and proof method are given for the first time through a force transformation of projecting the superposition chip thickness on a virtual cutting edge. On this basis, a fast estimation method and an accurate simulation method for force fluctuation prediction are established to quantify the intensity of force fluctuations under different parameters. Both two prediction methods and the experimental cutting tests validate the proposed theory effectively. The result shows a high potential of the proposed theory for studying the force behavior under different milling parameters or cutter parameters and at least 75% of the test workload can be reduced.

A Study on the Influence of Tire Speed and Pressure on Measurement Parameters Obtained from High-Speed Tire Uniformity Testing

In order to improve the test conditions of the tire uniformity test and the effect of the speed and tire pressure on the uniformity parameters, the uniformity test of the tire under different speeds and tire pressure was carried out by a high-speed uniformity test machine, and the experimental data were analyzed and fitted by the regression analysis method. This paper introduces the definition of uniformity and the uniformity parameters of automotive tires; the working principle of a high-speed uniformity testing machine is briefly described, a mathematical model of the uniformity testing machine is established, and the signal acquisition process of the tire uniformity parameters and the calculation method of the uniformity parameters are described. The test result indicates: As the speed increases, the radial force fluctuation, lateral force fluctuation, tangential force fluctuation, and turning torque fluctuation of the tire increase, and the positive torque fluctuation first increases and then decreases; with the increase of tire pressure, the radial force fluctuation and the tangential force fluctuation of the tire increase, and the lateral force fluctuation, the turning torque fluctuation, and the returning moment fluctuation are all reduced. Compared to the low speed uniformity test, the high speed uniformity test can better reflect the uniformity of the tire, reducing the speed of the vehicle can reduce the radial runout and lateral sway of the tire; increasing the tire pressure can reduce the left and right swing of the vehicle.