负泊松比超材料因其在受拉时横向膨胀、受压时横向收缩的反常力学行为,在航空航天、生物医疗和柔性电子等领域具有重要应用潜力。然而,现有研究多集中于二维或三维各向同性设计,难以满足实际工程中对材料方向相关性的需求。本文提出一...负泊松比超材料因其在受拉时横向膨胀、受压时横向收缩的反常力学行为,在航空航天、生物医疗和柔性电子等领域具有重要应用潜力。然而,现有研究多集中于二维或三维各向同性设计,难以满足实际工程中对材料方向相关性的需求。本文提出一种基于密度法的三维正交各向异性负泊松比超材料拓扑优化设计方法,通过构建新的多目标优化函数,结合均质化理论,实现单胞结构在3个正交方向上的负泊松比性能。首先,基于SIMP(solid isotropic material with penalization)材料插值模型,引入几何约束条件,在确保优化单胞对称性的同时有效减少计算规模;其次,通过惩罚函数建立了新的目标函数及优化模型;最后,利用周期性边界条件下的有限元均质化方法,计算等效力学性能,并通过灵敏度分析驱动设计变量更新。数值算例表明,优化后的单胞在3个主方向上均实现了负泊松比性能。本研究为三维正交各向异性拉胀超材料的可控制备提供了理论依据,扩展了机械超材料的设计和应用范围。展开更多
Ultrasonic treatment and hydrothermal method were applied in the traditional homogeneous precipitation for nano-TiO_2 preparation, which was used as carrier material for the production of honeycomb selective catalytic...Ultrasonic treatment and hydrothermal method were applied in the traditional homogeneous precipitation for nano-TiO_2 preparation, which was used as carrier material for the production of honeycomb selective catalytic reduction(SCR) catalyst. The influence rules of the two improved methods on characterization of TiO_2 samples, denitration activity and mechanical strength of honeycomb SCR catalyst samples were mainly focused on. The results indicate that the specific surface area, particle size and uniformity of TiO_2 samples are significantly improved by both of the ultrasonic and hydrothermal treatments compared with the traditional homogeneous precipitation. Also, the denitration activities of catalyst samples are enhanced by the two improved methods(the NO_x reduction ratio increases from 88.89% to 95.45% by ultrasonic homogeneous precipitation process, and to 94.12% by hydrothermal homogeneous precipitation process). On the other hand, because of good spherical shape and high particle distribution of TiO_2 sample from hydrothermal homogeneous precipitation process, the corresponding honeycomb catalyst samples get the best mechanical strength, which is even higher than that of the reference sample from commercial nano-TiO_2. So, it is concluded that the hydrothermal homogeneous precipitation can be a feasible and effective preparation method of TiO_2 carrier for the honeycomb SCR catalyst production.展开更多
文摘负泊松比超材料因其在受拉时横向膨胀、受压时横向收缩的反常力学行为,在航空航天、生物医疗和柔性电子等领域具有重要应用潜力。然而,现有研究多集中于二维或三维各向同性设计,难以满足实际工程中对材料方向相关性的需求。本文提出一种基于密度法的三维正交各向异性负泊松比超材料拓扑优化设计方法,通过构建新的多目标优化函数,结合均质化理论,实现单胞结构在3个正交方向上的负泊松比性能。首先,基于SIMP(solid isotropic material with penalization)材料插值模型,引入几何约束条件,在确保优化单胞对称性的同时有效减少计算规模;其次,通过惩罚函数建立了新的目标函数及优化模型;最后,利用周期性边界条件下的有限元均质化方法,计算等效力学性能,并通过灵敏度分析驱动设计变量更新。数值算例表明,优化后的单胞在3个主方向上均实现了负泊松比性能。本研究为三维正交各向异性拉胀超材料的可控制备提供了理论依据,扩展了机械超材料的设计和应用范围。
基金Project(201031)supported by the Environmental Protection Scientific Research of Jiangsu Province,ChinaProject(BE2010184)supported by the Technology Support Program of Jiangsu Province-Industrial Parts,China
文摘Ultrasonic treatment and hydrothermal method were applied in the traditional homogeneous precipitation for nano-TiO_2 preparation, which was used as carrier material for the production of honeycomb selective catalytic reduction(SCR) catalyst. The influence rules of the two improved methods on characterization of TiO_2 samples, denitration activity and mechanical strength of honeycomb SCR catalyst samples were mainly focused on. The results indicate that the specific surface area, particle size and uniformity of TiO_2 samples are significantly improved by both of the ultrasonic and hydrothermal treatments compared with the traditional homogeneous precipitation. Also, the denitration activities of catalyst samples are enhanced by the two improved methods(the NO_x reduction ratio increases from 88.89% to 95.45% by ultrasonic homogeneous precipitation process, and to 94.12% by hydrothermal homogeneous precipitation process). On the other hand, because of good spherical shape and high particle distribution of TiO_2 sample from hydrothermal homogeneous precipitation process, the corresponding honeycomb catalyst samples get the best mechanical strength, which is even higher than that of the reference sample from commercial nano-TiO_2. So, it is concluded that the hydrothermal homogeneous precipitation can be a feasible and effective preparation method of TiO_2 carrier for the honeycomb SCR catalyst production.
