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In order to study the air gap magnetic field distribution and torque of axial-flux solid magnetic couplers with 9 pairs of permanent magnets, a layer model is firstly introduced, which divides the couplers into conductive and non-conductive areas. The two-dimensional magnetic scalar potential method is derived to solve the magnetic field strength in conductive areas and the magnetic scalar potential in non-conductive areas. Carter coefficient is introduced to correct the 3D end effects, and the formula of air gap flux density and torque is derived. Then， the distribution of 3D air gap magnetic field, eddy current and the influence of different working parameters on the characteristics of the torque are obtained by the finite element simulation software. Finally, a measure system of three-dimensional magnetic field and the magnetic drive experimental platform are built to measure the 3D air gap magnetic field and the torque. The experimental results are in good agreement with the results of theoretical calculation and the simulation analysis, which shows that the formula of the air gap flux density and the torque have high accuracy and can be used as a reference for further research on the transmission characteristics of eddy-current magnetic couplers.

Aiming at the speed regulation characteristics of slotted-type eddy-current couplers, the expression of the induced magnetic field generated by the induced eddy current is derived by using Ampère's law and the induced magnetic field is introduced into the equivalent magnetic circuit model. Then, the calculation formula of electromagnetic torque is derived in combination with Kirchhoff's law. The electromagnetic torque formula is combined with the expression of constant torque load and quadratic rate load respectively, and the theoretical formula of the speed regulation relationship under corresponding load conditions is obtained. The 3D finite element simulation and experiment are used to verify the proposed theoretical model of speed regulation. It is found that the proposed theoretical model has good accuracy in the case of small air gap length.

In order to study the transmission performance of slotted-type eddy-current couplers with radial misalignment, based on the theory of the equivalent magnetic charge theory, the copper which cuts the magnetic field line in motion is equivalent to permanent magnet. Combining with Coulomb's law, a calculation model of output torque is established in this study. The analysis of magnetic flux density, copper loss and output torque of couplers are all simulated by finite element software, and the maximum allowable value of radial misalignment is obtained. The results show that with the increase of radial misalignment, the induced magnetic field decreases during operation, which results in the increase of the magnetic flux density, the decrease of the copper loss and the torque, and the fluctuations of the copper loss and the output torque changing with time become more and more obvious. When the radial misalignment is less than 6 mm, the torque generated by the couplers can almost be remained accurately and the fluctuation of the torque is relatively stable.

In order to solve the problem of calculating the air gap magnetic field and torque of slotted-type magnetic couplers, a subdomain analysis model is introduced. The magnetic couplers are divided into five regions along the axis, the boundary equations are established at the interfaces of each region. According to the alternating arrangement characteristics of yoke teeth and the conductor and the vector magnetic potential formulas in yoke teeth and the copper conductor disk are deduced respectively. Due to the end effect, Schwarz-Christoffel mapping is used to modify the coefficient of the flux density at the end face of the cogging. On the basis of obtaining the vector magnetic potential of the yoke iron and conductor respectively, the formulas of the air gap magnetic field and electromagnetic torque are deduced. The structure parameters of the slotted-type magnetic couplers are substituted into the theoretical model to calculate the axial air-gap magnetic field distribution and mechanical characteristic curves. By comparing the results with those obtained by finite element simulation, the accuracy of the theoretical model is verified and the cause of the error is analyzed.

The Global Positioning System (GPS) and the Global Navigation Satellite System (GLONASS) have been used to estimate ocean tide loading displacement (OTLD) with high accuracy; however, GPS has been problematic at K2 and K1 frequencies because they coincide with the GPS orbital period and revisit period, and GLONASS with an ambiguous float performs best for the two aforementioned constituents in the north and up directions. Here, we investigated the potential of using the BeiDou Navigation Satellite System (BDS) constellation [the medium Earth orbit (MEO) satellite revisit period of seven sidereal days, distinct from K1] to improve the accuracy of the eight major ocean tide loading constituents. BDS and combined GPS+BDS OTLD estimations are improved based on the algorithm of GPS kinematic precise point positioning (PPP), and all of them resolve ambiguity. Data from 72 continuously operating Global Navigation Satellite System (GNSS) reference stations distributed in Fujian Province from 2017 to 2020 were collected and processed to produce OTLD parameters for each of the three modes: GPS, BDS, and GPS+BDS. To investigate whether considering the effect of second-order ionosphere (Ion2) delays improved the tidal constituents, the Ion2 delays were used to calculate the OTLD parameters, and the results demonstrated that Ion2 delays improved four solar/sidereal constituents (S2, K2, K1, and P1). By comparing the root-mean-square misfits between the reference values and the GNSS OTLD estimates, the results showed that the reference/GPS+BDS misfits of most constituents were the lowest among the three components, except for K1 and P1. Meanwhile, reference/BDS misfits for the K1 and P1 constituents are all less than 0.6 mm, demonstrating that BDS estimation can improve the accuracy for K1 and P1 in three directions, particularly for the east component. The phasor plots also show that GPS, BDS, and GPS+BDS show poor agreement for the K2 constituent. BDS agrees with the reference model at the 95% confidence level, whereas GPS and GPS+BDS do not agree with the reference model for the K1 constituent. We then propose the use of a combination of constellation modes to determine the OTLD parameters: GPS+BDS for five constituents (M2, N2, O1, Q1, S2) and BDS-only solutions for the K1 and P1 constituents. The K2 constituent, which is problematic in GPS+BDS solutions and requires the help of GLONASS or Galileo, avoids orbital errors over a 12 h period. [ABSTRACT FROM AUTHOR]

Rivers are important carriers of water transmission, water supply, and water nourishment, and the virtuous cycle of their ecosystems is directly related to the degree of completion of the construction of ecological civilization and the high-quality development of the national economy. From the perspective of symbiosis theory, this paper constructs a river health value assessment index system and analyzes the symbiotic synergistic effect of nine provinces in the Yellow River Basin in China from 2000 to 2020 by using a logistic symbiosis evolution model. Health values at the Yellow River Basin scale and the provincial administrative area scale were also analyzed, and it was found that (1) the Yellow River Basin experienced a period of sub-par river health in the past, but with the implementation of ecological protection and high-quality development strategy in recent years, the health of the river showed an trend of improvement during the period of 2017–2020; (2) at the provincial administrative scale, the Yellow River Basin has significant differences, which are manifested in the obvious differences between provinces in terms of the functional value of river health provision and the economic functional value. In order to reduce the regional differences, it is recommended that the provinces work together and give full play to their own characteristics and strengths in the management of the watershed, so as to make up for the weaknesses of regional development and realize the synergistic development of the watershed; and (3) in terms of symbiosis level, rivers in the Yellow River Basin generally show parasitic relationships, and most of them exhibit natural ecological diversity and competitiveness with socio-economics. Therefore, a more comprehensive consideration of the balanced development of each function is needed in river health management in the future to achieve integrated watershed health. These results suggest that the development of river ecological health in the Yellow River Basin requires the joint efforts of the whole of society as well as regional synergy and integrated management at the policy level to achieve more sustainable and balanced watershed development. [ABSTRACT FROM AUTHOR]

State‐of‐health (SOH) estimation is essential for evaluating the aging process of lithium‐ion batteries, which can effectively guarantee the steady application of the battery system. Most existing prediction approaches apply a single model or a single feature to achieve SOH estimation based on the entire charging curve. In this paper, a multifeature‐based stacked ensemble learning framework is proposed for SOH prediction using partial charging curves. Firstly, combined with the range of state‐of‐charge (SOC) commonly used in the actual operation of vehicles, the charging segment is effectively intercepted through the mapping correlation between the SOC and the terminal voltage. Then, five relevant features characterizing the battery health status are extracted from multiple data, such as temperature, voltage, and incremental capacity profiles. Finally, a two‐level stacking ensemble framework is developed to fuse several individual estimation methods for higher SOH accuracy. To validate the performance of the proposed method, the Oxford University data set and the NASA data set are deployed for comparison experiments, and the results reveal the superior precision and robustness of the developed model in SOH estimation. [ABSTRACT FROM AUTHOR]