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After over 60 years of development, the space propulsion field in China has made tremendous progress in terms of technology system and product pedigree, and has supported major engineering applications including manned spaceflight, applied satellites, and deep space exploration. However, considering the requirements of future major aerospace missions in China, the technical level of current space propulsion systems is still insufficient, and it is urgent to plan directions for the innovative development and breakthroughs of the field. This study reviews the development status of the space propulsion systems from the aspects of electric, chemical, nuclear, and new-concept space propulsion, and analyzes the requirements of future applications. Specifically, high-performance, low-cost space propulsion systems are required to support the networking of low-Earth-orbit (LEO) small satellites; high-thrust, reusable low-temperature chemical propulsion technologies are required for new space-transportation systems; and multi-type, long-life space propulsion technologies are required for deep-space applications. The results demonstrate that the space propulsion field in China still faces multiple challenges. First, the system reliability and lifespan require further improvement. Second, the space propulsion systems of China still lag behind the advanced international level in terms of product maturity of some technologies. Third, this field typically has a high product cost. Fourth, there are few types of optional technologies, and the research progress of key technologies is lagging. Therefore, we propose the following suggestions: (1) optimizing technology options through top-level planning, (2) improving the development mechanism of the field by emphasizing basic research, and (3) clarifying and promoting scientific research and development in key technological directions, thereby achieving in-orbit applications of the propulsion systems for LEO small satellites, Earth–Moon space transfer, and deep space exploration (including manned spaceflight).

The combination method of numerical simulation and experimental verification was used to optimize the current evaluation method of tear strength of rubber unnicked angle test piece. Firstly, the tear energy at angle position of rubber test piece with different clamp distances was simulated by the simulation software, and then advanced video extensometer-digital image correlation analysis software was used to obtain the strain distribution cloud nephograms and the multi-location strain curves of the test piece with time. A new method was proposed to evaluate comprehensively the unnicked angle tear property by combining strain distribution cloud nephogram and corrected tear strength, and the method applicability was verified by the tear strength test of pure natural rubber and natural rubber/synthetic rubber blends. The results showed that the tensile degree of the non-effective test region and the tear energy at angle position were all different with the different clamp distances, when the other para-meters of the test piece were the same, which increased the volatility of the test results. Compared with the standard currently in effect, the variation coefficient of parallel test results could be reduced by using the corrected tear strength, and the test results was positively correlated with the carbon black dispersion in the vulcanizates.

Granary is an important facility to ensure the safety of grain storage. The granary is a large closed space with dim lighting and poor air circulation. Operations such as fumigation and air conditioning increase personnel safety risks. The identification and analysis of abnormal behaviors of workers through security videos in the granary has become a key safe operations for workers as an important technical guarantee. This paper proposed a video recognition algorithm for abnormal behavior of workers in a granary based on a skeleton sequence multi-algorithm. First, the YOLOv3tiny model was used to quickly detect the human body, combined with Sort to track the motion trajectories of multiple targets, and the human skeleton coordinate sequence and weight information were extracted through the AlphaPose model. Then, based on the real spacial graph (RSG) composed of natural connection nodes of the human skeleton and virtual spacial graph (VSG) constructed by interconnecting the center of gravity of the virtual human body with the head, hands, and feet, the bin was extracted based on the balance of the interaction between the center of gravity of the human body dynamics and the hands and feet. Spatial characteristics of abnormal behavior of internal workers and spatiotemporal characteristics of concatenated temporal convolution (TC). Finally, a virtual-real combining spatial temporal graph convolution network (VR-STGCN) video recognition algorithm for abnormal behavior of granary workers was proposed. At the same time, a hybrid dataset was built, and comparative experiments and analysis were conducted between VR-STGCN and four algorithms such as SSD, PCANet, Two-StreamCNN, and STGCN. The results showed that all indicators of VR-STGCN were better than those of the other four algorithms. VR-STGCN can accurately identify abnormal behaviors such as falling, crawling, and lying down of people in the granary in complex environments such as insufficient light, multiple targets, and long distances. The recognition accuracy reached 97.7%, and the processing speed was 18.67fps, which can analyze the abnormal behavior of workers in real time. The research results could provide a new and efficient technology for the safety of granary workers in complex environments.

This exploratory study aims to explore how theory of mind (ToM) of children of Zhuang (the largest ethnic minority in China) is acquired and refined. The sample included 83 Zhuang Chinese (M.sub.age = 4.52 yrs, SD = 0.86 yrs, 40 boys) and 136 Han Chinese (M.sub.age = 4.38 yrs, SD = 0.82 yrs, 62 boys) preschool children. The current study revealed that both ethnic groups fitted the Western, individualist ToM acquisition pattern, in contrast to previous studies conducted in other cities in China revealed that Chinese children fitted the Asian, collectivistic ToM acquisition pattern. Moreover, our data showed that there was no difference in executive function and ToM link between two ethnic groups. Specifically, children's age, receptive language, working memory, and inhibitory control skills were positive predictors for two groups of children's ToM performance. By analyzing variances within a developing country that has been undergoing rapid social changes since the 1980s, these findings help to provide a more comprehensive socio-cultural understanding of mental states. They also emphasize the value of exposing children to multi-ethnic societies that might provide children with more opportunities to perceive, think, and reason about other ethnic groups' mental states., Author(s): Xiao-Hui Hou [sup.1] [sup.2] [sup.3] , Yao Liu [sup.1] [sup.2] , Ying Li [sup.1] [sup.2] , Ling-Yu Wang [sup.4] Author Affiliations: (1) https://ror.org/04dx82x73, grid.411856.f, 0000 0004 1800 2274, Laboratory [...]