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The problem of cultivated land soil quality in the Huaihe River Basin has become increasingly prominent. How to accurately and quantitatively evaluate the soil quality of regional cultivated land and realize its efficient use has become an urgent problem. In order to explore the spatial autocorrelation and variation in soil nutrients in cultivated land in the plain of Fengtai County in the Huaihe River Basin, a total of 306 soil samples and mature wheat samples were collected in the study area to analyze soil pH, total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), available potassium (AK) and slow-release potassium (SK) content and wheat biomass, and combined with geostatistical methods and GIS technology. The Kriging interpolation method and Moram's I index method were systematically analyzed. Principal component analysis (PCA) and Pearson correlation analysis were used to establish the minimum data set (MDS) of soil quality, which was used to calculate the soil quality index (SQI) and determine the key factors affecting soil quality. The results showed that the soil pH was in weak variation, and the other nutrient indexes were in medium variation. The spatial variability of soil-available potassium nutrients was affected by random factors such as human activities and structural factors such as soil parent materials. The spatial autocorrelation of organic matter, total nitrogen, alkali-hydrolyzable nitrogen, available phosphorus, available potassium and mitigation potassium was weak, which was mainly affected by random factors such as human activities. An unequivocal positive spatial nexus was discerned across all nutrients. Cumulatively, the nutrient dispersion across the investigated territory was somewhat diffuse, manifesting in a mosaic pattern with pronounced zonal nutrient allocation disparities in the meridional, median, and septentrional segments. An explicit latitudinal dichotomy delineating zones of nutrient opulence and paucity was also observed. These insights can pave the way for tailored fertilization strategies and judicious pedological stewardship in Fengtai County. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) pollution in soil has become a huge problem for agricultural production in China and even the world. Passivation and phytoremediation are two important remediation technologies for Cd pollution. In this study, the cadmium-contaminated and phosphorus-poor farmland soil around a mining area in Huainan was taken as the research object, and the remediation effect of biochar and phosphorus-containing materials on soil cadmium pollution was discussed. The results showed that the combined application of biochar and phosphorus-containing materials significantly reduced the pH of non-rhizosphere soil and rhizosphere soil, and increased the content of soil dissolved organic carbon (DOC). The combined application of biochar and phosphorus-containing materials significantly reduced soil pore water Cd and soil available Cd. In addition, both a single application of biochar and synergistic application of biochar and phosphorus-containing materials significantly increased the biomass of aboveground and underground parts of amaranth and soil urease and catalase activities. Phosphorus application reduced the bioavailability of Cd in soil. With the increase in phosphorus application, the content of available Cd in soil decreased significantly, and there was a certain negative correlation between Cd content and phosphorus content in plants. The abundance of beneficial microorganisms such as Ochrobactrum, Anaerolinea, Achromobacter, and Cellvibrio in soil was significantly increased after the synergistic application of biochar and phosphorus-containing materials. [ABSTRACT FROM AUTHOR]

Double planetary gear trains (DPGTs) have high loading capacity and transmission, making them indispensable in various heavy rotating machinery applications. However, the presence of planetary gear-set radial bearing roller dimension deviation (PBRDD) from real-world manufacturing discrepancies poses a significant challenge to the dynamics of the DPGTs. Previous dynamic models often overlooked the internal excitations of the planetary gear-set radial bearing, focusing only on the single planetary gear train dynamics, rendering them inadequate for studying the impact of the PBRDD on DPGTs. Therefore, this paper proposes a coupling method integrating the PBRDD model with the DPGT dynamic model, taking into consideration the planetary gear-set radial bearing’s internal excitations, to reveal the impact of PBRDD on DPGTs’ dynamics. Specifically, the changes in roller–ring contact force and roller–cage collision force induced by PBRDD are considered. Through comprehensive simulation and experimental analyses, the accuracy of the dynamic model is assessed and its efficacy in capturing the effects of PBRDD on DPGTs’ dynamics is validated. The results show that the DPGTs’ dynamics increment with the increment of PBRDD. [ABSTRACT FROM AUTHOR]

AbstractAs an important component of rotating machinery, the rotor system (RSM) has a decisive effect on the system dynamics. Most previous works established the RSM dynamic model without the bearing slip, ball dynamics, and cage dynamics. This work proposes a flexible rotor system (FRSM) dynamic model with the bearing slip, ball dynamics, and cage dynamics. The effect of the bearing slip on the FRSM dynamic is analyzed. The FRSM consists of the rotor, rigid disk, and ball bearings. The rotor is modeled using the Timoshenko beam elements. The dynamic models of the rigid disk and ball bearing are established by using the lumped parameter method. The bearing clearance and installation method effects are considered. An experimental verification is developed to demonstrate the validity of the proposed dynamic model. The results obtained by the proposed model and the previous model without the bearing slip are compared. Moreover, the effects of the rotor rotational speed and rigid disk unbalance eccentric distance on the FRSM dynamics and bearing slip are analyzed. The results shows that rotor rotation frequency (fs) is not obvious for health FRSM and the amplitudes of fs and nfs increase with rotation speed and unbalance eccentric distance, which can provide guidance for fault diagnosis. [ABSTRACT FROM AUTHOR]

In the propulsion shaft systems, the bearings could support the complicated load conditions due to the unbalanced magnetic pull of the motor together with the propeller thrusts. The contact characteristics and skidding behaviors of balls could aggravate. The previous dynamic models of individual ball bearings subjected to the constant load cannot accurately simulate the phenomenon. To overcome this problem, a tribo-dynamic model of a flexible propulsion shaft system is proposed. The real-time contact characteristics and skidding and spinning behaviors of bearings for a propulsion shaft system are calculated based on Newmark-β and Runge–Kutta methods. The bearings' power losses are numerically estimated. The main power loss components for the system in different rotation speed conditions are located. The effects of the preload and bearing structural parameters (raceway radius, number of balls, initial contact angle) on the bearings' power losses are discussed. The results indicate that applying appropriate preload on the supporting bearings and reducing the ball number of thrust bearings can be efficient methods for system power loss reduction. [ABSTRACT FROM AUTHOR]