From technology importation to independent innovation, Chinese High speed railway (HSR) has been rapidly developed in the past a few years. However, this technology development mode introduces very complex electromagnetic environment of HSR system, which is based on various equipment with different Electromagnetic compatibility (EMC) design. Consequently, the suppression of electromagnetic disturbance and the electromagnetic protection is becoming an urgent issue for HSR. The characteristics of traction power supply technology, train operation control technology and other core technologies are quite unique in Chinese HSR. In this paper, the EMC and the electromagnetic safety issue of Chinese HSR is discussed, which is derived from technology development mode and core technology characteristics. The limitation of the high speed train's exportation due to the lack of test method for the train's emission is also analyzed. Combining the electromagnetic environment characteristic and the development planning of Chinese HSR, several suggestions in the research of antielectromagnetic interference, electromagnetic protection in the strong electromagnetic field and the whole large system's radiation emission test method are put forward.

Many efforts have been taken in recent years to push atomic gravimeters toward practical applications. We demonstrate an atomic gravimeter named NIM-AGRb2 that is transportable and suitable for high-precision gravity measurements. Constraint-structured active vibration isolation (CS-AVI) is used to reduce the ground vibration noise. The constraint structure in CS-AVI ensures that the isolation platform only has vertical translation, with all other degrees of freedom (DoFs) being constrained. Therefore, the stability of active vibration isolation is enhanced. With the implementation of CS-AVI, the sensitivity of NIM-AGRb2 reached as low as 20.5 μGal/Hz^1/2. The short-term sensitivity could be further reduced to 10.8 μGal/Hz^1/2 in a seismologic observation station. Moreover, we evaluated the system noise of the gravimeter, and the results were consistent with our observations.

The China high-speed trains use cable trays to neatly arrange the cables running through the distributed systems. On one hand, they protect cables against external electromagnetic interference and reduce external radiation from the cables. On the other hand, the cable trays create waveguide structures that affect the coupling among cables inside the cable trays. To simplify coupling analysis for cables going through a cable tray, a lumped circuit model was built using admittance blocks extracted from a mixed-potential integral equation (MPIE) formulation. In the MPIE formulation, either the half-free space or the waveguide dyadic Green's function was used depending on the region where the cables were. A test case was investigated. Results by the proposed circuit model were validated by measurement and full-wave simulation results.

This article concentrates on the steady-state thermal characteristics of the Axial-Radial Flux-Type Permanent Magnet Synchronous Motor (ARFTPMSM). Firstly, the three-dimensional mathematical models for electromagnetic calculation and analyses are established, and the machine loss, including the stator loss, armature winding loss, rotor loss, and axial structure loss is calculated by using time-step Finite Element Method (FEM). Then, the loss distribution is assigned as the heat source for the thermal calculation. Secondly, the mathematical model for thermal calculation is also established. The assumptions and the boundary conditions are proposed to simplify the calculation and to improve convergence. Thirdly, the three-dimensional electromagnetic and thermal calculations of the machine, of which the armature winding and axial field winding are developed by using copper wires, are solved, from which the temperature distributions of the machine components are obtained. The experiments are carried out on the prototype with copper wires to validate the accuracy of the established models. Then, the temperature distributions of machine components under different Axial Magnetic Motive Force (AMMF) are investigated. Since the machine is finally developing by using HTS wires, the temperature distributions of machine developed by utilizing High Temperature Superconducting (HTS) wires, are also studied. The temperature distribution differences of the machine developed by using copper wires and HTS wires are drawn. All of these above will provide a helpful reference for the thermal calculation of the ARFTPMSM, as well as the design of the HTS coils and the cryogenic cooling system.

The balise transmission system (BTS) is an automatic identification system for vehicle–ground communication based on radio frequency identification (RFID) technology. The electromagnetic coupling characteristics of BTS have a very important effect on the transmission quality of the uplink telegram signals. However, signal transmission problems of BTS often occur due to unreasonable installation mode or parameter setting. In order to solve these problems, it is necessary to fully discuss the electromagnetic coupling characteristics of the BTS. In this paper, the transmission process of energy and data between the onboard antenna unit and the balise was analyzed using digital twin technology. A high-precision dynamic electromagnetic coupling model of the BTS was established from four aspects of three-dimensional structure, physical properties, behavior patterns, and rule restrictions. Then the accuracy of the model was verified by experiments. Finally, the influence of typical parameters on the uplink signal is calculated and analyzed quantitatively. The results showed that compared with other factors discussed in this paper, the vertical distance and the installation mode had greater effects on the uplink signal. These results can be used to guide the engineering installation and related optimization of the BTS.

Frequency measurements for complex single-tone signals under additive Gaussian noise cover extensive engineering fields. Existing direct discrete Fourier transform (DFT) interpolation methods suffer both degraded accuracies under noisy conditions and biased estimation performances for a restricted number of samples. To address these problems, this paper proposes a fast and accurate frequency estimation scheme using two-sample DFT interpolation. Firstly, this work introduces a frequency deviation detector that can exactly recognize the interpolation direction. Additionally, to correct the estimation biases of existing direct estimators, this paper further develops an unbiased and extremely accurate estimator for an arbitrary number of samples. Finally, a fast and accurate frequency estimation scheme is proposed based on the developed detector and estimator. Results of tests indicate that the proposed scheme exhibits good noise tolerance and can provide exact bias corrections for small and medium numbers of samples. The proposed strategy can provide superior precision and serve as an efficient frequency estimation scheme in various engineering fields.