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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.

Prefabricated buildings (PBs) are a new type of building construction, which are less time-consuming and cause low environmental pollution and resource consumption. They play an important role in industrialized construction and clean production and have gained worldwide attention. However, the high construction costs have become a major obstacle to their popularity and application. This study investigates the factors influencing construction costs of PBs in China using a systematic literature review (SLR), fuzzy interpretive structure modeling (fuzzy ISM), and the Matrice d’Impacts croises-multiplication appliqué an classment (MICMAC) technique. First, 32 influencing factors were identified from the SLR. Second, out of which 16 critical factors were selected and mapped in a hierarchical model through semi-structured interview screening, and the MICMAC technique was used to classify the cost-influencing factors of PBs into different categories. The results revealed that all identified factors played pivotal roles in various capacities and influenced the cost of PB construction. This study may assist administrators and policymakers in better understanding the factors that influence the costs of PBs construction to manage and reduce them. [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]

To improve the efficiency of estimation of deriving OTLD parameters with higher accuracy and take full advantage of multi-GNSS data, we investigate the potential of using global ocean tide model predictions as prior constraint for GLONASS and combined GPS+GLONASS kinematic precise point positioning (PPP), analyzing one year of GPS and GLONASS data from 20 Crustal Movement Observation Network China (CMONC) sites distributed along China coast. Seven global ocean tide models predictions are employed as prior constraint in kinematic PPP. Compared with the results of GPS-only kinematic PPP with priori information constraint, the result shows that GPS+GLONASS and GLONASS can improve the accuracy of OTLD estimates more than 40% in three components over GPS. The comparison of the effect of OTLD estimates on long-period signals in position time series shows that the correction effect of the kinematic PPP with seven different priori information constraint estimates is all as same as the reference model in three components. [ABSTRACT FROM AUTHOR]