Taking a certain area in Sichuan Province as the object of this study, this paper adopts fuzzy mathematics method to make an evaluation on ecological risks of heavy metal in soil of this area. On calculation of factor...Taking a certain area in Sichuan Province as the object of this study, this paper adopts fuzzy mathematics method to make an evaluation on ecological risks of heavy metal in soil of this area. On calculation of factors’ weights, the traditional method of giving weight according to pollutants’ concentrations fails to consider the toxicity of heavy metals, and can’t reflect their actual ecological effect. With reference to the toxicity coefficient in potential ecological risk index evaluation, this article revises the traditional fuzzy mathematics evaluation model and puts forward a new method to calculate factors’ weight by incorporating toxicity levels in weight setting. The results of this study indicate: surface soil of this area was good in general, with 91.2% samples belonging to the first level, 7.77% samples belonging to the second level, and only 1.03% belonging to the third level. Compared with the results of the evaluation method of the reality content of soil, soil quality is better than the results of the quantitative evaluation, and is closer to the actual local conditions.展开更多
Even when damaged by injury or disease bone tissue has the remarkable ability to regenerate.When this process is limited by large size bone defects,tissue engineering is responsible for restoring,maintaining or improv...Even when damaged by injury or disease bone tissue has the remarkable ability to regenerate.When this process is limited by large size bone defects,tissue engineering is responsible for restoring,maintaining or improving tissue function.Scaffolds are support structures,designed to be implanted in the damaged site,supporting mechanical loads and protecting the regenerating bone tissue.In this paper,3D-printed PLA scaffolds with three different porosity values and two different geometries were experimentally and numerically characterized.Micro-CT analysis showed that fused filament fabrication can be used to produce scaffolds with the desired porosity and 100%of interconnected pores.Under monotonical compression,scaffolds apparent compressive modulus increased from 89 to 918 MPa,while yield stress increased from 2.9 to 27.5 MPa as porosity decreased from 70 to 30%.Open porosity decreased up to 8%on aligned scaffolds and 14%on staggered scaffolds,after compression,while scaffold’s surface-to-volume ratio highest reduction(7.48 to 4.55 mm−1)was obtained with aligned low porosity scaffolds.Micro-CT volume reconstruction allowed for scaffold simplified numerical models to be built and analyzed.Excellent agreement was found when predicting scaffold’s apparent compressive modulus.Overall,it can be concluded that 3D printing is a viable scaffold manufacturing technique for trabecular bone replacement.展开更多
文摘Taking a certain area in Sichuan Province as the object of this study, this paper adopts fuzzy mathematics method to make an evaluation on ecological risks of heavy metal in soil of this area. On calculation of factors’ weights, the traditional method of giving weight according to pollutants’ concentrations fails to consider the toxicity of heavy metals, and can’t reflect their actual ecological effect. With reference to the toxicity coefficient in potential ecological risk index evaluation, this article revises the traditional fuzzy mathematics evaluation model and puts forward a new method to calculate factors’ weight by incorporating toxicity levels in weight setting. The results of this study indicate: surface soil of this area was good in general, with 91.2% samples belonging to the first level, 7.77% samples belonging to the second level, and only 1.03% belonging to the third level. Compared with the results of the evaluation method of the reality content of soil, soil quality is better than the results of the quantitative evaluation, and is closer to the actual local conditions.
基金This work was supported by FCT,through IDMEC under LAETA(project UIDB/50022/2020)CeFEMA(UID/CTM/04540/2019)+1 种基金CERENA(UIDB/04028/2020)IPFN activities also received financial support from FCT through Projects UIDB/50010/2020 and UIDP/50010/2020.
文摘Even when damaged by injury or disease bone tissue has the remarkable ability to regenerate.When this process is limited by large size bone defects,tissue engineering is responsible for restoring,maintaining or improving tissue function.Scaffolds are support structures,designed to be implanted in the damaged site,supporting mechanical loads and protecting the regenerating bone tissue.In this paper,3D-printed PLA scaffolds with three different porosity values and two different geometries were experimentally and numerically characterized.Micro-CT analysis showed that fused filament fabrication can be used to produce scaffolds with the desired porosity and 100%of interconnected pores.Under monotonical compression,scaffolds apparent compressive modulus increased from 89 to 918 MPa,while yield stress increased from 2.9 to 27.5 MPa as porosity decreased from 70 to 30%.Open porosity decreased up to 8%on aligned scaffolds and 14%on staggered scaffolds,after compression,while scaffold’s surface-to-volume ratio highest reduction(7.48 to 4.55 mm−1)was obtained with aligned low porosity scaffolds.Micro-CT volume reconstruction allowed for scaffold simplified numerical models to be built and analyzed.Excellent agreement was found when predicting scaffold’s apparent compressive modulus.Overall,it can be concluded that 3D printing is a viable scaffold manufacturing technique for trabecular bone replacement.
