Biomechanical behaviors of dragonfly wing: relationship between configuration and deformation

In this paper, the natural structures of a dragonfly wing, including the corrugation of the chordwise cross-section, the sandwich microstructure veins, and the junctions between the vein and the membrane, have been investigated with experimental observations, and the morphological parameters of these structural features are measured. The experimental result indicates that the corrugated angle among the longitudinal veins ranges from 80° to 150°, and the sandwiched microstructure vein mainly consists of chitin and protein layers. Meanwhile, different finite element models, which include models I and I^* for the planar forewings, models II and II^* for the corrugated forewings, and a submodel with solid veins and membranes, are created to investigate the effects of these structural features on the natural frequency/modal, the dynamical behaviors of the flapping flight, and the deformation mechanism of the forewings. The numerical results indicate that the corrugated forewing has a more reasonable natural frequency/modal, and the first order up-down flapping frequency of the corrugated wing is closer to the experimental result (about 27.00 Hz), which is significantly larger than that of the planar forewing (10.94 Hz). For the dynamical responses, the corrugated forewing has a larger torsional angle than the planar forewing, but a lower flapping angle. In addition, the sandwich microstructure veins can induce larger amplitudes of torsion deformation, because of the decreasing stiffness of the whole forewing. For the submodel of the forewing, the average stress of the chitin layer is much larger than that of the protein layer in the longitudinal veins. These simulative methods assist us to explain the flapping flight mechanism of the dragonfly and to design a micro aerial vehicle by automatically adjusting the corrugated behavior of the wing.     

CuO-SiO_2和Cu_2O-SiO_2薄膜的制备及其光学性能

以CuSO_4·5H_2O和正硅酸乙酯为前驱体,配制了稳定透明的Cu~(2+)-SiO_2复合溶胶电解液。采用电化学-溶胶凝胶方法,在恒电位-0.9 V下得到Cu-SiO_2复合膜,该复合薄膜分别在250和450℃的热处理后得到Cu_2O-SiO_2和CuO-SiO_2复合薄膜。采用XRD、SEM/EDX和台阶仪表征了复合薄膜的组成、形貌和厚度;采用紫外-可见光谱和Z扫描技术研究了复合薄膜的线性和三阶非线性光学性能。结果表明Cu2O-SiO_2和CuO-SiO_2复合薄膜中的Cu含量、Cu的形态(如Cu_2O、CuO)及Cu_2O或CuO颗粒大小影响薄膜的光学带隙和三阶非线性光学性能,2种薄膜的光学带隙分别是2.67和2.54 eV,三阶非线性极化率χ(3)分别为2.31×10~(-6)和1.36×10~(-6) esu。     

CuO-SiO2和Cu2O-SiO2薄膜的制备及其光学性能

以CuSO₄·5H₂O和正硅酸乙酯为前驱体,配制了稳定透明的Cu²⁺-SiO₂复合溶胶电解液。采用电化学-溶胶凝胶方法,在恒电位-0.9 V下得到Cu-SiO₂复合膜,该复合薄膜分别在250和450℃的热处理后得到Cu₂O-SiO₂和CuO-SiO₂复合薄膜。采用XRD、SEM/EDX和台阶仪表征了复合薄膜的组成、形貌和厚度;采用紫外-可见光谱和Z扫描技术研究了复合薄膜的线性和三阶非线性光学性能。结果表明Cu₂O-SiO₂和CuO-SiO₂复合薄膜中的Cu含量、Cu的形态（如Cu₂O、CuO）及Cu₂O或CuO颗粒大小影响薄膜的光学带隙和三阶非线性光学性能,2种薄膜的光学带隙分别是2.67和2.54 eV,三阶非线性极化率χ^（3）分别为2.31×10^-6和1.36×10^-6 esu。     

Biomechanical behaviors of dragonfly wing:relationship between configuration and deformation

In this paper,the natural structures of a dragonfly wing,including the corrugation of the chordwise cross-section,the sandwich microstructure veins,and the junctions between the vein and the membrane,have been investigated with experimental observations,and the morphological parameters of these structural features are measured.The experimental result indicates that the corrugated angle among the longitudinal veins ranges from 80 to 150,and the sandwiched microstructure vein mainly consists of chitin and protein layers.Meanwhile,different finite element models,which include models I and I for the planar forewings,models II and II for the corrugated forewings,and a submodel with solid veins and membranes,are created to investigate the effects of these structural features on the natural frequency/modal,the dynamical behaviors of the flapping flight,and the deformation mechanism of the forewings.The numerical results indicate that the corrugated forewing has a more reasonable natural frequency/modal,and the first order up-down flapping frequency of the corrugated wing is closer to the experimental result(about 27.00 Hz),which is significantly larger than that of the planar forewing(10.94 Hz).For the dynamical responses,the corrugated forewing has a larger torsional angle than the planar forewing,but a lower flapping angle.In addition,the sandwich microstructure veins can induce larger amplitudes of torsion deformation,because of the decreasing stiffness of the whole forewing.For the submodel of the forewing,the average stress of the chitin layer is much larger than that of the protein layer in the longitudinal veins.These simulative methods assist us to explain the flapping flight mechanism of the dragonfly and to design a micro aerial vehicle by automatically adjusting the corrugated behavior of the wing.