Search

Background: In response to the current needs for the development of large-scale wheat combine harvesters, this paper carried out the structure design and performance test of a large feed volume wheeled wheat combine harvester. Methods: Based on the characteristics of wheat plants, this paper designed a wheeled wheat combine harvester with a feed rate of 10kg/s. Subsequently, the structural parameters and design process of the main working components such as the header feeding device, the conveying device, the threshing device, the separation and cleaning device, the walking device, the cab, and the straw crushing device are elaborated. The strength of the key parts was checked by finite element simulation, and the structural parameters were optimized. Results: The results show that the large feed volume combine harvester which designed in this paper can achieve entrainment loss rate of less than 2.39% and cleaning loss rate of less than 0.26%, significantly lower than the current 3% loss rate and there is almost no unclean and broken situation. Conclusion: This research provides reference for the design of large feed volume combine harvester.

Microglia are important immune cells in the central nervous system. There is growing interest in the study of microglia due to their implication in neurodevelopment, acute injury, and neuropsychiatric disorders. They undergo birth, death, and regeneration during the lifetime. Although data on the ontogeny of microglia have been studied for decades, the birth and repopulation of microglia remain legendary and mysterious. In this review, we discuss recent studies that provide new insights into the origin and regeneration of microglia. Modulating the development of microglia may offer new therapeutic opportunities for preventing deleterious effects of inflammation and controlling excessive inflammation in brain diseases.

In view of the fact that the design of the cab structure of wheeled combine harvesters in China lacks ergonomic design parameters exclusive for Chinese drivers, there are generally problems such as high vibration and poor comfort of the whole machine structure during the harvesting process. Firstly, this paper designed the cab structure of a wheeled grain combine harvester based on ergonomics. Then, the driver's handling comfort and visibility were simulated and analyzed using Creo. Finally, the relevant dimensions of the driver's control device were optimized. The results show that the wheeled grain combine harvester cab based on ergonomic design better meets their driving comfort needs. In addition, it is found that the operating frequencies of the key components, such as the main shaft of the conveyor spindle, the vibrating screen, the threshing drum, and the intermediate shaft of the engine, partially overlap with the frequency of human discomfort. Therefore, modal planning is also needed for this harvester to meet human comfort requirements better. This paper provides the basic parameters for the design of the cab structure of the combine harvester with high comfort for the Chinese harvesting machinery driver.

As a multi-source vibration machine, the complex vibration of the combine harvester has caused many effects on various components. In this paper, the dynamic response of the plate and shell on the combine harvester is studied, and the influence of various factors on the vibration of the plate and shell is determined. The structure of the plate and shell is optimized, and the scheme of structural optimization that replaces the finite element model with the surrogate model is developed. The structure is designed with Latin hypercube design (LHD), the model of response surface is generated based on the Kriging model, and then the parameters are optimized by a multi-objective genetic algorithm (MOGA). It is realized that the first-order natural frequency of the plate is increased by 14.6% under the same mass, avoiding the resonance range of the main excitation of the machine. At the same time, its dynamic response under the multi-point force is also greatly decreased by 62.4%.

Single-shot carrier envelope phase (CEP) measurement is a challenge in the research field of ultrafast optics. We theoretically investigate how an intense terahertz pulse modulates second harmonic emission (SH) from a gas plasma induced by a few-cycle laser pulse (FCL). Results show that the modulation quantity of SH intensity has a cosinoidal dependence on the CEP of FCL pulses, based on which we propose a low energy, all-optical method for single-shot CEP measurements via using a known intense terahertz pulse. Moreover, we propose an experimental realization.

A drained solution is derived for cylindrical cavity expansion in modified Cam-clay soils under biaxial in-situ stresses. The problem is formulated by solving a system of first-order differential equations using an auxiliary variable, which provides semi-analytical expressions for stresses and specific volume. The solution validity is examined through comparisons with the existing solution and the finite element simulation. The results show that the elastic-plastic boundary of cylindrical cavity expanding under biaxial in-situ stresses is an ellipse, due to the existence of shear stress. Besides, the stress distribution and the stress path change significantly with the variation of radial direction.