We explored the home learning environments of 173 Mexican preschool children in relation to their numeracy performance. Parents indicated the frequency of their formal home numeracy and literacy activities, and their academic expectations for children’s numeracy and literacy performance. Children completed measures of early numeracy skills. Mexican parent–child dyads from families with either high- or low-socioeconomic status participated. Low-SES parents reported higher numeracy expectations than high-SES parents, but similar frequency of home numeracy activities. In contrast, high-SES parents reported higher frequency (...) of literacy activities. Path analyses showed that operational numeracy activities were positively related to children’s numeracy skills in the high- but not in the low-SES group. These findings improve the understanding of the role of the home environment in different contexts and provide some insights into the sources of the variable patterns of relations between home learning activities and children’s numeracy outcomes. They also suggest that SES is a critical factor to consider in research on children’s home numeracy experiences. (shrink)

In this article, based on the previous works, a new fractional-order financial model is put up. The chaotic behavior of the fractional-order financial model is suppressed by designing an appropriatePDϑcontroller. By choosing the delay as the bifurcation parameter, we establish the sufficient condition to guarantee the stability and the existence of Hopf bifurcation of fractional-order financial model. Also, the influence of the delay and the fractional order on the stability and the existence of Hopf bifurcation of fractional-order financial model is (...) revealed. An example is given to confirm the effectiveness of the analysis results. The main findings of this article play an important role in maintaining economic stability. (shrink)

Individuals' capacity to participate in leisure activities is contingent upon their ability to overcome obstacles. It is worthwhile to investigate how individuals perceive constraints on their leisure activities participation during the COVID-19 pandemic. This study demonstrates that the connotation of leisure constraints during pandemic includes personal health concerns, shock on economic revenue, reduced freedom of travel, and inconvenience associated with epidemic prevention. Reduced travel freedom is the most influential factor on participation intentions, followed by personal health concerns. Significant differences in (...) perceptions of constraints are observed between groups with different characteristics. (shrink)

Tree branches near the electric power transmission lines are of great threat to the electricity supply. Nowadays, the tasks of clearing threatening tree branches are still mostly operated by hand and simple tools. Traditional structures of the multirotor aerial robot have the problem of fixed structure and limited performance, which affects the stability and efficiency of pruning operation. In this article, in order to obtain better environmental adaptability, an active deformable trees-pruning aerial robot is presented. The deformation of the aerial (...) robot is implemented through two ways, arm telescopic and folding. In order to suppress the influence of internal and external disturbances on the system, Active Disturbance Rejection Control technology is adopted to build the flight controller. Firstly, active deformation aerial robot structure is given, followed by system dynamic model establishment under wind disturbance using the Newton–Euler method. Also, the analysis of the gusts influence on the system is considered. Then, the active deformation aerial robot system is decoupled into a combination of six SISO systems, so that a disturbance rejection controller is designed. Finally, the expanded state observer and the nonlinear state error feedback law are used to inspect and compensate the disturbance. Simulation results of attitude and position tracking as well as the antidisturbance capability show that the active deformation aerial robot with the ADRC flight controller designed in this paper has excellent attitude control capabilities during flight and trees-pruning operation. (shrink)

This article elaborates the conditions as well as four potential modes of the ecological problem: (1) The mode of the absolute minimization of the ecological problem: minimum population plus minimum Gross Domestic Product (GDP), which is characterized by the quantity of destruction being less than the quantity of natural rehabilitation of an ecosystem. This mode is the poorest mode with minimum change. (2) The mode of the relative minimization of the ecological problem: minimum population plus maximization of GDP, which is (...) characterized by the quantity of destruction being less than the quantity of both natural rehabilitation and human rehabilitation of an ecosystem. This mode is the best mode with minimum change. (3) The mode of the relative maximization of the ecological problem: maximization of population plus minimum GDP, which is characterized by the quantity of destruction to the ecosystem not being offset by the quantity of human rehabilitation. An example of this mode is an underdeveloped district with vast population and limited farmland. (4) The mode of the absolute maximization of the ecological problem: maximization of population plus maximization of GDP. This is characterized by the continuous increase of the quantity of destruction beyond the quantity of both natural rehabilitation and human rehabilitation of the ecosystem. Its final outcome is the collapse of the ecosystem and a catastrophe to human beings. (shrink)