Abstract With the continuous advancement of space exploration missions, the mechanical environment for planetary detectors is becoming increasingly severe. As a result, fatigue, fracture, large deformation and other forms of failures are more likely to occur at the load-bearing structures. As a critical part of the load-bearing structure of a goat, goat tibia has remarkable toughness because of its unique microstructures. In this investigation, firstly, the cortical bone of goat tibia was observed by SEM, and the characteristic microstructures in different regions were identified. Secondly, the cross section of cortical bone was loaded by long-term inplane stress, then the toughness of cortical bone in different regions are obtained and compared based on the orientation and distribution of cracks after the load. Thirdly, a simplified FEM model mimicking typical microstructure of the cortical bone is proposed using cohesive modeling, and then the toughening mechanism of the typical microstructure is validated with numerical simulation. Finally, the toughening mechanisms of cortical bone were discussed according to the SEM observation as well as the numerical simulation. This study of the toughening mechanism of cortical bone can be helpful for the biomimetic design of high-toughness structures.
To provide experience for formulating prevention and control policies, this study analyzed the effectiveness of the Coronavirus disease 2019(COVID-19) prevention and control policies, and evaluated health equity and epidemic cooperation among BRICS countries.This study summarized the pandemic prevention and control policies in BRICS countries and evaluated the effectiveness of those policies by extracting COVID-19 related data from official websites.As of May 4, 2021, responding to COVID-19. China adopted containment strategies. China's total confirmed cases (102,560) were stable, without a second pandemic peak, and the total deaths per million (3.37) were much lower than others. India and South Africa who adopted intermediate strategies have similar pandemic curves, total confirmed cases in India (20,664,979) surpassed South Africa (1,586,148) as the highest in five countries, but total deaths per million (163.90) lower than South Africa (919.11). Brazil and Russia adopted mitigation strategies. Total confirmed cases in Brazil (14,856,888) and Russia (4,784,497) continued to increase, and Brazil's total deaths per million (1,936.34) is higher than Russia (751.50) and other countries.This study shows BRICS countries implemented different epidemic interventions. Containment strategy is more effective than intermediate strategy and mitigation strategy in limiting the spread of COVID-19. Especially when a strict containment strategy is implemented in an early stage, but premature relaxation of restrictions may lead to rebounding. It is a good choice to combat COVID-19 by improving the inclusiveness of intervention policies, deepening BRICS epidemic cooperation, and increasing health equities.
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