In the present paper, a series of hierarchical warping functions is developed to analyze the static and dynamic problems of thin walled composite laminated helicopter rotors composed of several layers with single clos...In the present paper, a series of hierarchical warping functions is developed to analyze the static and dynamic problems of thin walled composite laminated helicopter rotors composed of several layers with single closed cell. This method is the development and extension of the traditional constrained warping theory of thin walled metallic beams, which had been proved very successful since 1940s. The warping distribution along the perimeter of each layer is expanded into a series of successively corrective warping functions with the traditional warping function caused by free torsion or free beading as the first term, and is assumed to be piecewise linear along the thickness direction of layers. The governing equations are derived based upon the variational principle of minimum potential energy for static analysis and Rayleigh Quotient for free vibration analysis. Then the hierarchical finite element method. is introduced to form a,. numerical algorithm. Both static and natural vibration problems of sample box beams axe analyzed with the present method to show the main mechanical behavior of the thin walled composite laminated helicopter rotor.展开更多
A theoretical method for static analysis of naturally curved and twisted beams under complicated loads was presented, with special attention devoted to the solving process of governing equations which take into accoun...A theoretical method for static analysis of naturally curved and twisted beams under complicated loads was presented, with special attention devoted to the solving process of governing equations which take into account the effects of torsion-related warping as well as transverse shear deformations. These governing equations, in special cases, can be readily solved and yield the solutions to the problem. The solutions can be used for the analysis of the beams, including the calculation of various internal forces, stresses, strains and displacements. The present theory will be used to investigate the stresses and displacements of a plane curved beam subjected to the action of horizontal and vertical distributed loads. The numerical results obtained by the present theory are found to be in very good agreement with the results of the FEM results. Besides, the present theory is not limited to the beams with a double symmetric cross-section, it can also be extended to those with arbitrary cross-sectional shape.展开更多
为实现脑卒中患者手功能康复情况的自动、精准定量评估,本文提出一种基于手部骨骼的手势识别与功能评估方法。首先,利用MediaPipe框架提取手部关键点并连接形成手骨骼模型,将传统的RGB视频数据集转化为手骨骼数据集。然后,通过C3D模型...为实现脑卒中患者手功能康复情况的自动、精准定量评估,本文提出一种基于手部骨骼的手势识别与功能评估方法。首先,利用MediaPipe框架提取手部关键点并连接形成手骨骼模型,将传统的RGB视频数据集转化为手骨骼数据集。然后,通过C3D模型进行训练,实现手功能动作的识别。最后,在正确识别的基础上进一步评估,采用动态时间规整(dynamic time warping,DTW)算法,在实现时序对齐的同时引入空间对齐机制,通过计算患者健侧手与患侧手完成同一动作的DTW距离,量化动作执行的相似度,为每个动作找到最佳阈值作为定量评估的标准。实验结果表明,用骨骼数据代替传统视频数据,使手势识别的准确率提升至99.01%,缩短了训练时间,并结合DTW算法,实现了手功能康复情况的自动评估。展开更多
基金The project supported by the National Natural Science Foundation of China (19932030)
文摘In the present paper, a series of hierarchical warping functions is developed to analyze the static and dynamic problems of thin walled composite laminated helicopter rotors composed of several layers with single closed cell. This method is the development and extension of the traditional constrained warping theory of thin walled metallic beams, which had been proved very successful since 1940s. The warping distribution along the perimeter of each layer is expanded into a series of successively corrective warping functions with the traditional warping function caused by free torsion or free beading as the first term, and is assumed to be piecewise linear along the thickness direction of layers. The governing equations are derived based upon the variational principle of minimum potential energy for static analysis and Rayleigh Quotient for free vibration analysis. Then the hierarchical finite element method. is introduced to form a,. numerical algorithm. Both static and natural vibration problems of sample box beams axe analyzed with the present method to show the main mechanical behavior of the thin walled composite laminated helicopter rotor.
文摘A theoretical method for static analysis of naturally curved and twisted beams under complicated loads was presented, with special attention devoted to the solving process of governing equations which take into account the effects of torsion-related warping as well as transverse shear deformations. These governing equations, in special cases, can be readily solved and yield the solutions to the problem. The solutions can be used for the analysis of the beams, including the calculation of various internal forces, stresses, strains and displacements. The present theory will be used to investigate the stresses and displacements of a plane curved beam subjected to the action of horizontal and vertical distributed loads. The numerical results obtained by the present theory are found to be in very good agreement with the results of the FEM results. Besides, the present theory is not limited to the beams with a double symmetric cross-section, it can also be extended to those with arbitrary cross-sectional shape.
文摘为实现脑卒中患者手功能康复情况的自动、精准定量评估,本文提出一种基于手部骨骼的手势识别与功能评估方法。首先,利用MediaPipe框架提取手部关键点并连接形成手骨骼模型,将传统的RGB视频数据集转化为手骨骼数据集。然后,通过C3D模型进行训练,实现手功能动作的识别。最后,在正确识别的基础上进一步评估,采用动态时间规整(dynamic time warping,DTW)算法,在实现时序对齐的同时引入空间对齐机制,通过计算患者健侧手与患侧手完成同一动作的DTW距离,量化动作执行的相似度,为每个动作找到最佳阈值作为定量评估的标准。实验结果表明,用骨骼数据代替传统视频数据,使手势识别的准确率提升至99.01%,缩短了训练时间,并结合DTW算法,实现了手功能康复情况的自动评估。
