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Precise and timely prediction of crop yields is crucial for food security and the development of agricultural policies. However, crop yield is influenced by multiple factors within complex growth environments. Previous research has paid relatively little attention to the interference of environmental factors and drought on the growth of winter wheat. Therefore, there is an urgent need for more effective methods to explore the inherent relationship between these factors and crop yield, making precise yield prediction increasingly important. This study was based on four type of indicators including meteorological, crop growth status, environmental, and drought index, from October 2003 to June 2019 in Henan Province as the basic data for predicting winter wheat yield. Using the sparrow search algorithm combined with random forest (SSA-RF) under different input indicators, accuracy of winter wheat yield estimation was calculated. The estimation accuracy of SSA-RF was compared with partial least squares regression (PLSR), extreme gradient boosting (XG-Boost), and random forest (RF) models. Finally, the determined optimal yield estimation method was used to predict winter wheat yield in three typical years. Following are the findings: 1) the SSA-RF demonstrates superior performance in estimating winter wheat yield compared to other algorithms. The best yield estimation method is achieved by four types indicators’ composition with SSA-RF) (R2= 0.805, RRMSE= 9.9%. 2) Crops growth status and environmental indicators play significant roles in wheat yield estimation, accounting for 46% and 22% of the yield importance among all indicators, respectively. 3) Selecting indicators from October to April of the following year yielded the highest accuracy in winter wheat yield estimation, with an R2of 0.826 and an RAISEof 9.0%. Yield estimates can be completed two months before the winter wheat harvest in June. 4) The predicted performance will be slightly affected by severe drought. Compared with severe drought year (2011) (R2= 0.680) and normal year (2017) (R2= 0.790), the SSA-RF model has higher prediction accuracy for wet year (2018) (R2= 0.820). This study could provide an innovative approach for remote sensing estimation of winter wheat yield, yield.

Wind power gears will be excessively worn due to lubrication failure during operation. Herein, the tribological properties of rubbing pairs are improved by filling solid lubricants into surface texture. In texture design, three types of topological textures (Circle (C), Hexagon (H) and Circle/Hexagon (CH)) were obtained by cell topology optimization, and then three cases with 20%, 30%, and 40% density were designed for each texture. Next, SnAgCu and TiC were deposited in texture of AISI 4140 steel (AS) to obtain 9 kinds of self-lubricating surfaces. Among them, AS with 30% CH density (AS-CH30) exhibits excellent mechanical and tribological properties. Compared with AS-C and AS-H, the maximum equivalent stress of AS-CH was decreased by 10.86% and 5.37%, respectively. Friction coefficient and wear rate of AS-CH30 were 79.68% and 78% lower than those of AS. The excellent tribological performances of AS-CH30 can be attributed to the synergistic effect of topological surface and solid lubricants. Topological surface can not only reduce fluctuation of equivalent stress, but also promote the stored lubricants to be easily transferred at the contact interface to form a 200 nm lubricating film containing solid lubricants (mainly), oxides and wear debris.

To enhance the performance and longevity of bearings by addressing the issue of insufficient lubrication, this research paper introduces a multi-drive lubrication system. Inspired by the micro-texture of clamshells, bionic textured surfaces (BTSs) were designed and fabricated. Calcium complex grease (CCG), aluminum complex grease (ACG), lithium complex grease (LCG), and these three greases containing 2wt.% accordion-like MXenes Ti3C2were prepared, respectively. This study commits to evaluating the tribological properties of BTSs with different densities under different grease lubrication. The results showed that BTSs (ρ= 38%) had the best anti-friction and anti-wear under the MXenes lithium complex grease lubrication, the average friction coefficient (0.113) and wear rate reached the smallest (10.5×10−7mm3N−1m−1), and only slight wear occurred. This was mainly attributed to the synergistic and complementary lubricating effects of BTSs and MXenes-enhanced grease.

To improve the tribological performance of CSS-42L bearing steel, smooth surfaces (SSs), groove-textured surfaces (GSs), GSs with Sn-Ag-Cu (GSs-SAC), and GSs with Sn-Ag-Cu-Ti3C2(GSs-SACT) were prepared on CSS-42L. In addition, experimental studies were conducted on tribological properties. The obtained results indicated that GSs-SACT exhibited the best anti-friction and noise reduction performances. These remarkable tribological performances were attributed to the synergistic effects of grooves, Sn-Ag-Cu, and MXene-Ti3C2. The inconsistent rules of frictional forces were improved by the grooves and SACT, which inhibit the friction-induced noise. The micro-nano size-effects of MXene-Ti3C2enhanced the repairing effect and anti-friction property of composite lubricants, which improved the profile characteristics of GSs-SACT.

•A rare case of primary mediastinal malignant meningioma was reported.•Gene sequencing and clonal evolution analysis can help to find suitable therapeutic targets.•FGF6 amplification mutation can promote the progression of malignant meningioma.•FGF6 gene amplification may be a target for using anlotinib.

Pre-stressed hardening grinding (PSHG) can control the residual stress after grinding, and its surface layer has impacting hardening (IH) effect besides the well-known quenching hardening effect due to the impact of abrasive grain. In order to study its IH, the paper established the IH model of PSHG using ANSYS simulation method considering the main factors of grinding impacting. The IH characteristic and mechanism was revealed. The IH effect mainly concentrates on the surface layer and reduces rapidly along the direction of depth. It increases with the increase of pre-stress and the grinding depth due to their comprehensive promotion of dislocation, dynamic recovery of crystal grain and motion characteristic of the iron atom. The IH experiment of PSHG was carried on and the simulation model was verified by and large. The model can reveal the IH characteristic accurately.

Point grinding uses the point contact to shape surface topography of workpiece which has high machining precision. Its surface topography has a close relation with its service performance. In order to study the topography of point grinding, these authors carried out the experiment and established a new assessing model based on the correlation function method. The inner characteristics of topography are revealed by self-correlation and mutual correlation function method and its mechanism is analyzed. The study shows that the topography of point grinding has obvious periodical portions, which means it is consistent and uniform. The mutual correlations of every direction show the surface topography of point grinding is isotropic. Point grinding surface has better consistency under larger included angle and smaller grinding depth. And it has better isotropy under larger included angle. Surface roughness has the opposite rule from the consistency and isotropy. The influence of point grinding angle on surface topology is much larger than grinding depth.

The elastic and plastic deformations have significant effect on the tribological properties of the graphene-reinforced Ni3Al matrix self-lubricating composites. The primary purpose of this study is to investigate the tribological behavior and wear mechanisms of graphene-reinforced Ni3Al matrix self-lubricating composites by researching the effects of different loads and the corresponding friction heat on the elastic or plastic deformation. The dry sliding tribology tests of graphene-reinforced Ni3Al matrix self-lubricating composites are carried out at the loads of 7, 10, 13, and 16N, respectively. The elastic or plastic deformation is judged by comparing the yield stress with the contact stress analyzed by the numerical simulation method. It is found that graphene-reinforced Ni3Al matrix self-lubricating composites exhibit good tribological properties at 13 N due to the elastic deformation, leading to the formation of relatively stable wear resistant layer. Graphene-reinforced Ni3Al matrix self-lubricating composites show poor tribological performance at 16 N for the plastic deformation, resulting in the destruction of the wear resistant layer and the generation of surface cracks and material spalling. From the mechanical mechanism of wear, the plastic deformation and thermal stress are the important factors to lead to the material spalling. The results could be used to guide the selection of suitable working conditions for having good tribological performance of low wear and long service life.

In order to analyze the effects of frictional heat on the tribological performance of Ni3Al matrix self-lubricating composite containing 6.2 vol.% graphene nanoplatelets (NB), the dry sliding friction tests of Ni3Al-based alloy and NB against GCr15 steel ball are undertaken under different loads from 3 to 18 N. The effects of different amount of frictional heat on the friction and wear mechanism of NB are also studied. The results show that tribological performance of NB is better than that of Ni3Al-based alloy under same working conditions. The addition of graphene nanoplatelets promotes the formation of stable glaze layer on worn surface. In addition, graphene nanoplatelets enhance the thermal conductivity of NB, which makes the surface temperature of wear scar of NB in a proper range (about 413 ℃) at 13 N and avoids the serious friction and wear caused by the accumulation of frictional heat. At 13 N, NB shows the lower friction coefficient (0.32) and wear rate (3.6 × 10−5mm3·N−1·m−1). It is attributed to the appropriate local temperature (about 413 ℃) of worn surface, resulting in the formation of stable glaze layer with good friction reducing and wear resistance on worn surface. This study was meaningful for optimizing applied loads to realize the appropriate frictional heat and good tribological behavior of NB.

It was significant to study the longevity of mechanical component by analyzing the effect of friction layer on the predicting models of wear rates and friction coefficients. In this study, based on the changes in applied load Fand testing temperature T, the friction and wear behaviors of TiAl-10 wt.% Ag were carried out sliding against Si3N4ball (6 mm in diameter). At 0–80 min, the prediction models of friction coefficients and wear rates were constructed by the method of bivariate rational interpolation. The predicting accuracies of Pcomp-f: 94–98.7% (friction coefficient) and Pcomp-w: 87.7–98.5% (wear rate) indicated that the constructed prediction model was able to evaluate the friction coefficients and wear rates of TiAl-10 wt.% Ag. The high predicting accuracies were mainly attributed to the excellent plastic fluidity of silver, the smooth morphology of wear scar, and the friction layer of low grain strain.

In this study, the friction and wear behavior of NiAl alloy containing graphene nanoplatelets (NG) under different sliding velocities were investigated. NG shows the better tribological performance, if compared to NiAl-based alloy without graphene nanoplatelets (NA). In the range of sliding velocities varying from 0.2 to 1.2 m/s, the formation of glaze layer in NG could be easily distinguished. The beneficial effect of graphene nanoplatelets (GNPs) for the formation of glaze layer of NG is obvious, if compared to NA, resulting in the reduction of friction and improvement of wear resistance of NG. Moreover, a suitable higher sliding velocity will be better for the formation of glaze layer, but the wear rate will gradually increase with the increase of sliding velocity. It can be concluded that GNPs hold great application prospect as an effective solid lubricant to improve the tribological performance of NiAl alloys.

This study reports that small amounts of MoO3multilayer ribbon crystal (MoO3MLRC) in Ni3Al intermetallics showed the decreased friction coefficients and improved wear resistance at different contact loads. Specifically, the friction coefficients (0.32–0.34) and wear rates [(2–4) × 10−5mm3N−1m−1] are significantly reduced for Ni3Al at 2–8 N. A possible explanation for the friction and wear reduction is that MoO3MLRC as a multilayer material shears easily in the tribo-layer during the sliding contact, and provides low friction. In addition, this MoO3MLRC with excellent bending strength is found to dissipate shear stress and suppress severe plastic deformation under a cyclic stress, thus drastically improving wear resistance of Ni3Al.

Grinding hardening (GH) is a common processing method and pre-stressed hardening grinding (PSHG) is presented combined with the advantages of grinding hardening and pre-stress grinding. In order to study their hardening and transformation mechanism, the paper carried on the GH and PSHG experiments. According to the results, the hardening mechanism in GH was reanalysed through the point of classical nucleation theory. And the coupling relationship of stress, temperature and microstructure in PSHG is studied as well. The study shows: the dislocation in the grinding area compensates the negative factors of cooling speed during GH, so the hardening effect is remarkable. In PSHG, the parent-phase-hardening and strain-inducing-phase-changing due to applying pre-stress have comprehensive effect on the martensitic phase transformation in the grinding process. The characteristic of microstructure in hardening layer can be controlled by applying different pre-stress in PSHG.

To study the surface micro-topography in pre-stressed dry grinding process, the single grain cutting simulations were carried out in DEFORM-3D, besides, dry grinding experiments were conducted. The residual stress, groove depth and pile-up height were analysed in the simulations. The surface roughness was measured, and micro-surface topography was observed by SEM in the experiments. The results indicated that the application of pre-stress is beneficial to generate more compressive stress, which is beneficial to restrain the generation of surface micro-cracks. Pre-stress can reduce the pile-up height. When pre-stress is within a lower range, the groove depth decreases with pre-stress increasing, however, once pre-stress overcomes a certain value, surface fold appears and surface roughness increases instead. The influence rules of the cutting depth and feeding speed on surface micro-topography in pre-stressed dry grinding process are consistent with them in the traditional grinding process.

To study tribological enhancements of MXene-Ti3C2 under harsh environmental conditions (acidification, emulsification, and high-temperature oxidation), the textured CSS-42L bearing steel surfaces filled with Sn-Ag-Cu-Ti3C2 (TSs-SACT) were prepared. Under harsh conditions, lubrication properties of TSs-SACT were investigated. The results showed that the vibrations of frictional forces and loads of TSs-SACT with the best antifriction performance were suppressed. The curves of instantaneous frictional forces of TSs-SACT were the smoothest, and the amplitudes of instantaneous loads were reduced. Sn-Ag-Cu-Ti3C2 with good adsorption could inhibit the oil film ruptures, which improves the lubrication. TSs-SACT induced the tribochemical reactions to produce the intermetallic compounds and oxides with good tribological properties, resulting in the uniform profiles with excellent antifriction performance and wear resistance.

Grains have the impacting effect to the surface materials in grinding. In order to study the impact in the grinding process, the paper carried on the simulation by using DEFORM-3D software and conducted the grinding hardening experiment. It simulated the impact to the surface materials which was functioned by single grain and got the distribution of stress field of internal workpiece, analysed the equivalent stress and strain rate of surface of workpiece in the grinding process. It shows the analysis of equivalent stress reflected that grinding force is made up of a lot of surging force. The analysis of strain rate indicated that the impact and hardening effect to the surface of workpiece by grains is remarkable existing. The results of the experiment verified the correctness of simulation. DEFORM-3D simulation method could analyse and predict the parameter of surface hardened layer effectively.

To improve the antifriction and vibration reduction performances of oil-film bearings in hydroelectric generating set, textured CSS-42L surfaces filled with Sn-Ag-Cu-Ti3C2(TSs-SACT) were prepared, and the friction and vibration experiments under oil lubrication were carried out. The results showed that TSs-SACT with texture pitch of 600 μm and MXene of 5 wt.% (TSs-SACT(5%)-600) had the best antifriction, which reduced the fluctuation amplitudes of frictional forces and suppressed the friction-induced vibrations. The wear morphologies were improved by the synergistic effects of oil, grooves and Sn-Ag-Cu-Ti3C2, and TSs-SACT(5%)-600 with uniform profiles had the excellent wear resistance. The complexity of surface profiles could be characterized by fractal dimension, which can be enhanced by Sn-Ag-Cu-Ti3C2. TSs-SACT(5%)-600 with complex profiles keeps good antifriction during lubrication state transitions, which effectively improves the operation reliability of oil-film bearing in hydroelectric generating set.

A new approach to produce superfine WC-Co powder by direct reduction and carbonization is proposed. Water-soluble salts containing W and Co were used as raw materials. Tungsten and cobalt oxide powder (CoWO4/WO3) was first formed by a spray-pyrolysis technique, which was then mixed with carbon black and converted to WC-Co composite powder at 950°C for 4 h in N2 atmosphere. The resulting powder has a particle size of 100–300 nm.