Modeling, analysis, and optimization of dimensional accuracy of FDM-fabricated parts using definitive screening design and deep learning feedforward artificial neural network

Additive manufacturing(AM)technologies such as fused deposition modeling(FDM)rely on the quality of manufactured products and the process capability.Currently,the dimensional accuracy and stability of any AM process is essential for ensuring that customer specifications are satisfied at the highest standard,and variations are controlled without significantly affecting the functioning of processes,machines,and product structures.This study aims to investigate the effects of FDM fabrication conditions on the dimensional accuracy of cylindrical parts.In this study,a new class of experimental design techniques for integrated second-order definitive screening design(DSD)and an artificial neural network(ANN)are proposed for designing experiments to evaluate and predict the effects of six important operating variables.By determining the optimum fabrication conditions to obtain better dimensional accuracies for cylindrical parts,the time consumption and number of complex experiments are reduced considerably in this study.The optimum fabrication conditions generated through a second-order DSD are verified with experimental measurements.The results indicate that the slice thickness,part print direction,and number of perimeters significantly affect the percentage of length difference,whereas the percentage of diameter difference is significantly affected by the raster-to-raster air gap,bead width,number of perimeters,and part print direction.Furthermore,the results demonstrate that a second-order DSD integrated with an ANN is a more attractive and promising methodology for AM applications.

我国2017年中医类医院收入结构及地区差异性分析

[目的]探讨全国各地中医类医院的收入结构特点和差异,为政府制定适宜的中医药政策提供决策参考。[方法]根据《2017年全国中医药统计摘编》的数据,对各地区中医类医院的收入结构进行描述性统计和聚类分析。[结果]2017年我国中医综合医院医疗收入占总收入比重为86.6%,低于综合医院;而药品收入占医疗收入的比重为42.2%,其中基本药物占药品收入的比重为32.9%,均高于综合医院。全国各地中医类医院收入结构可分为四类地区,其中门诊收入占医疗总收入比重位于前三位的是北京(68.7%)、上海(59.7%)和天津(55.0%)。[结论]中医类医院与综合医院相比创收能力不足,药品收入比重较高,基本药物的使用情况更好,此外各地中医类医院业务开展存在明显的差异性。