Gongcheng Kexue Yu Jishu/Advanced Engineering Science

In recent years, the development of new energy vehicles industry is accelerating. Lithium nickel cobalt manganese/aluminum oxide ternary cathode materials (NCM/NCA), especially with the nickel content ≥50%, has aroused great interest in both academia and industry. This is mainly due to the fact that the aggregative parameters of performance and cost of NCM/NCA are superior to those of traditional cathode materials, such as LiCoO2 and LiFePO4. However, the application of NCM/NCA is affected by a number of drawbacks, including poor safety and insufficient cycle stability and so on, which are mainly attributed to its crystal and surface structure. Researchers have carried out various efforts to solve these problems and further improve the performance of NCM/NCA. Some remarkable results have been achieved in the past few years. In this review, the latest research progress on coating and doping of Ni-rich ternary cathode materials is summarized from the view on the mechanism of structural and electrochemical improvement of NCM/NCA. Finally, the perspective for the development of NCM/NCA cathode materials is also prospected.

The permeability characteristics of iron tailings are one of the important factors affecting the stability of the dam. The permeability coefficient is an important indicator of its permeability. Many formulas for calculating permeability coefficient have been proposed by scholars at home and abroad. However, these formulas are mostly applicable to coarse-grained soil, and its applicability to iron tailings is not clear. Therefor it is necessary to verify the accuracy of these formula and establish a calculation model for the permeability coefficient of iron tailings. The permeability properties of iron tailings sand were analyzed from various angles such as FC value, gradation, particle size, specific surface area and inter-particle void ratio with water head test in laboratory. The results showed that the permeability coefficient of iron tailings sand is affected by the fine content. The threshold of fine content is about 40%. The traditional formula for calculating the permeability coefficient was applied, but the results are inaccurate. The relationship among permeability coefficient of the iron tailings sand and the non-uniform coefficient Cu, the curvature coefficient Cc, the average particle size, the weighted average particle size, the volume ratio surface and the interparticle void ratio es is nonlinear. It is difficult to characterize the change of permeability coefficient when the fine content is large. However, the relationship between permeability coefficient of the iron tailings sand and the effective particle size and inter-particle void ratio is linear. A formula was developed for the determination of permeability coefficient of iron tailings sand by analyzing the effective particle size and inter-particle void ratio data. It is significant for the seepage field analysis and stability calculation of the Chenkeng tailings dam. This can be used to calculate the permeability coefficient of magnetite tailings.

The seismic effect created by blasting operations vibrates adjacent buildings and disturbs residents living in these buildings, often leading to disputes and complaints. In this paper, the vibration acceleration was calculated based on the measured blasting vibration velocity using the wavelet denoising-based four-point forward difference method. The infinite impulse response (IIR) digital filter was used to obtain the frequency weighting of acceleration, so as to calculate comfort assessment indexes such as vibration dose value (VDV), maximum weighted vibration severity (KBFmax and annoyance rate. Combined with the survey of engineering cases, comparative analysis was conducted on the indexes and standards that were suitable for the comfort assessment of blasting vibration. The results indicated that VDV, KBFmax, and annoyance rate indexes could all reflect the impact of blasting vibration on comfort to a certain extent, and that while the first two indexes could only be used for qualitative assessment, the annoyance rate index could be used for quantitative comfort assessment. In addition, by applying these assessment indexes for the comfort assessment of blasting vibration, preliminary control standards were provided.

A coupled dynamic model, which contains helical gears-shafts-bearings for a wind turbine gearbox transmission system, was built considering nonlinear factors of the time-varying mesh stiffness, the external varying load, and the dynamic transmission error at first. The model is confirmed to be right after comparing the theoretical data with the experimental load sharing values, and also it is found that the static load sharing is conservative to evaluate the non-equilibrium effect of a planetary gear system. Besides, the analyzing results of the influence of average error and amplitude error on the load sharing show that the load sharing could be decreased if the error goes up a little. Then, by means of treating the static tracing point as the dynamic initial values, we analyzed the initial position’s influence on the load sharing of transmission system to provide a theoretical basis of load sharing control. Furthermore, we explored the influence of high-speed shaft position angle on the load sharing and the dynamic load factor of gears fixed on the parallel shafts. The results provide useful theoretical guidelines for the design of parallel shaft gear system in the wind turbines.

In order to solve the modeling problems of saturated porous media, the engineering mixture theory was used to formulate the bulk constitutive theoretical framework of saturated porous media. Firstly, Supposing that the bulk deformation works of porous solid and fluid matrix were mutually independent and using Terzaghi’s effective spherical stress and pore pressure and fluid matrix pressure as stress state variables of constitutive model, the bulk stains expressions of solid phase and solid matrix and fluid matrix were obtained in the complementary energy.Secondly, the solid and fluid bulk constitutive equations of saturated porous cubes of balsawood in the loading and unloading stages were founded on the basis of the measuring data of model test conducted by Lade and de Boer. The calculating formulae of mechanical parameters were deduced such as solid bulk tangent modulus, Biot’s tangent coefficient and fluid Biot’s tangent modulus and so on. The change rules of mechanical parameters along with Terzaghi’s effective spherical stress and pore pressure were analyzed in the loading stage for solid bulk tangent modulus,Biot’s tangent coefficient and fluid Biot’s tangent modulus and so on. Finally, the one-dimensional consolidation equation of saturated porous media was derived from the bulk constitutive models of the paper and static balance equation. The consolidation behaviors of saturated porous cubes of balsawood were numerically analyzed and the change curves of consolidation degree and settlement with time were obtained. The researches show that, the solid bulk tangent modulus increased along with Terzaghi’s effective spherical stress and decreased along with pore pressure. The Biot’s tangent coefficient was between 0.42～0.95 and decreased along with Terzaghi’s effective spherical stress and pore pressure. The fluid Biot’s tangent modulus decreased firstly and then increased with Terzaghi’s effective spherical stress, and decreased with the increase of pore pressure. The tangent coefficient of pore pressure was less than 1.0 in most cases. The initial pore pressure was not equal to the external load in saturated porous media considering the compressibility of solid matrix. Thus the immediate settlement exists in saturated porous media after external load was applied. The modeling method in the paper can be used to model and numerically analyze nonlinear saturated porous media.