SLS快速成型技术中激光加工参数对制件翘曲变形的影响

通过制作专门的样件，采用正交实验的方差、极差分析方法，讨论主要加工参数的选取对翘曲变形的影响，认为研究加工参数对翘曲变形的影响规律，荻取合理的加工参数，可大幅度改善制作的成型精度。     

Preschool and primary school influences on the development of children's early numeracy skills between the ages of 3 and 7 years in Germany

Few studies have investigated how preschool and primary school interact to influence children's cognitive development. The present investigation explores German children's numeracy skills between age 3 (1st year of preschool) and age 7 (1st year of primary school). We first identified the influence of preschool experience on development while controlling for child factors, family background, and the quality of the home learning environment (HLE). We then considered how the instructional quality of primary schools influences numeracy. We finally analysed how preschool and primary school interact. We sampled 547 children who attended 97 German preschools. Latent growth curve analyses identified child and family factors related to age 3 numeracy and development to age 7: gender, migration background, socioeconomic status (SES), mother education, HLE. The effects of preschool on numeracy development persist until age 7 with notable effects from process quality. Strengthened efforts are needed to ensure high quality preschool education in Germany.