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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.

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]

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]

In this paper, a steady-state and dynamic response model is proposed to predict the working characteristics of the electromechanical transmission system including eddy-current magnetic couplers. Considering the influence of mechanical characteristics of motor and load device on the performance of eddy-current magnetic couplers, the system is divided into input and output for kinematic analysis. The expressions of electromagnetic torque versus speed are obtained through layer analysis of the eddy-current magnetic coupler during steady-state and then, the dynamic response model of the system is established by combining the kinematic analysis with the motor, the eddy-current magnetic coupler and three typical loads (constant torque load, quadratic rate load and constant power load). The dynamic characteristics during starting and speed-regulation of the system under constant torque loads are analyzed using the proposed model. The variations of the torque and speed with time of input and output are calculated by numerical integration. Finally, the speed and torque during starting and speed-regulation computed with the dynamic response model are compared with those obtained from the experimental results. The result shows a good agreement. [ABSTRACT FROM AUTHOR]