In recent years, high-altitude aerostats have been increasingly developed in the direction of multi-functionality and large size. Due to the large size and the high flexibility, new challenges for large aerostats have...In recent years, high-altitude aerostats have been increasingly developed in the direction of multi-functionality and large size. Due to the large size and the high flexibility, new challenges for large aerostats have appeared in the configuration test and the deformation analysis. The methods of the configuration test and the deformation analysis for large airship have been researched and discussed. A tested method of the configuration,named internal scanning, is established to quickly obtain the spatial information of all surfaces for the large airship by the three-dimensional(3D) laser scanning technology. By using the surface wrap method, the configuration parameters of the large airship are calculated. According to the test data of the configuration, the structural dimensions such as the distances between the characteristic sections are measured. The method of the deformation analysis for the airship contains the algorithm of nonuniform rational B-splines(NURBS) and the finite element(FE)method. The algorithm of NURBS is used to obtain the reconfiguration model of the large airship. The seams are considered and the seam areas are divided. The FE model of the middle part of the large airship is established. The distributions of the stress and the strain for the large airship are obtained by the FE method. The position of the larger deformation for the airship is found.展开更多
A six-variable geometrical nonlinear shear deformation laminatedtheory is presented by which normal stress and strain distributioncan be calculated. by considering some affective factors that wereneglected under the f...A six-variable geometrical nonlinear shear deformation laminatedtheory is presented by which normal stress and strain distributioncan be calculated. by considering some affective factors that wereneglected under the finite deformation condition, an improved vonKarman geometrical non- linear deformation-strain relation is usedfor large deformation analysis. After analyzing the bending problemof laminated plates, and comparing it with 3-D elasticity solutionsand J.N.Reddy five-vari- able simple higher-order shear deformationlaminated theory, we can conclude that a satisfactory cal- culationprecision has been achieved, which shows that is especially suitablefor the calculation in the condition of large deformation and thelaminated thick plate analysis.展开更多
目的:探讨慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)患者Ⅰ型胶原氨基端前肽(N-terminal propeptide of typeⅠprocollagen,PⅠNP)、Ⅰ型胶原羧基端肽β特殊序列(β-Cterminal telopeptide of typeⅠcollagen,β-C...目的:探讨慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)患者Ⅰ型胶原氨基端前肽(N-terminal propeptide of typeⅠprocollagen,PⅠNP)、Ⅰ型胶原羧基端肽β特殊序列(β-Cterminal telopeptide of typeⅠcollagen,β-CTX)水平与骨密度降低的关系。方法:选取COPD患者80例,分为COPD急性加重组40例与COPD稳定组40例,选取同期在本院体检的健康人群40例作为对照组,采用双能X射线骨密度检测仪测量所有对象的骨密度,测定并比较血清中骨代谢指标PⅠNP、β-CTX的水平。结果:COPD急性加重组与COPD稳定组骨质疏松发生率均明显高于对照组(P<0.001)。COPD急性加重组与COPD稳定组血清β-CTX水平较对照组均显著升高,且COPD急性加重组高于COPD稳定组,差异均有统计学意义(P<0.05);而COPD急性加重组与COPD稳定组血清PⅠNP水平、PⅠNP/β-CTX比值均低于对照组(P<0.01)。结论:COPD患者,尤其是急性加重期的患者,骨吸收功能异常活跃,新骨形成速度减慢,骨量丢失明显增加,从而存在较高的继发骨质疏松的风险。展开更多
A Jones-Nelson model has been applied to depict nonlinearstress-strain relations of composite laminae, where mechanicalproperties were expressed by strain energy density. The nonlin- earmaterial matrix is only a funct...A Jones-Nelson model has been applied to depict nonlinearstress-strain relations of composite laminae, where mechanicalproperties were expressed by strain energy density. The nonlin- earmaterial matrix is only a function of the strain energy density. Thena material model could be conveniently applied under complex stresscondition. In this paper, by introducing large displacementstress-strain measurement and varying-Poisson's ratio idea, animproved Jones-Nelson material model is presented, where theexpanding problem of material properties and convergence problems areover- come.展开更多
Simulation based structural reliability analysis suffers from a heavy computational burden, as each sample needs to be evaluated on the performance function, where structural analysis is performed. To alleviate the co...Simulation based structural reliability analysis suffers from a heavy computational burden, as each sample needs to be evaluated on the performance function, where structural analysis is performed. To alleviate the computational burden, related research focuses mainly on reduction of samples and application of surrogate model, which substitutes the performance function. However,the reduction of samples is achieved commonly at the expense of loss of robustness, and the construction of surrogate model is computationally expensive. In view of this, this paper presents a robust and efficient method in the same direction. The present method uses radial-based importance sampling (RBIS) to reduce samples without loss of robustness. Importantly, Kriging is fully used to efficiently implement RBIS. It not only serves as a surrogate to classify samples as we all know, but also guides the procedure to determine the optimal radius, with which RBIS would reduce samples to the highest degree. When used as a surrogate, Kriging is established through active learning, where the previously evaluated points to determine the optimal radius are reused. The robustness and efficiency of the present method are validated by five representative examples, where the present method is compared mainly with two fundamental reliability methods based on active learning Kriging.展开更多
基金supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (11421091)。
文摘In recent years, high-altitude aerostats have been increasingly developed in the direction of multi-functionality and large size. Due to the large size and the high flexibility, new challenges for large aerostats have appeared in the configuration test and the deformation analysis. The methods of the configuration test and the deformation analysis for large airship have been researched and discussed. A tested method of the configuration,named internal scanning, is established to quickly obtain the spatial information of all surfaces for the large airship by the three-dimensional(3D) laser scanning technology. By using the surface wrap method, the configuration parameters of the large airship are calculated. According to the test data of the configuration, the structural dimensions such as the distances between the characteristic sections are measured. The method of the deformation analysis for the airship contains the algorithm of nonuniform rational B-splines(NURBS) and the finite element(FE)method. The algorithm of NURBS is used to obtain the reconfiguration model of the large airship. The seams are considered and the seam areas are divided. The FE model of the middle part of the large airship is established. The distributions of the stress and the strain for the large airship are obtained by the FE method. The position of the larger deformation for the airship is found.
文摘A six-variable geometrical nonlinear shear deformation laminatedtheory is presented by which normal stress and strain distributioncan be calculated. by considering some affective factors that wereneglected under the finite deformation condition, an improved vonKarman geometrical non- linear deformation-strain relation is usedfor large deformation analysis. After analyzing the bending problemof laminated plates, and comparing it with 3-D elasticity solutionsand J.N.Reddy five-vari- able simple higher-order shear deformationlaminated theory, we can conclude that a satisfactory cal- culationprecision has been achieved, which shows that is especially suitablefor the calculation in the condition of large deformation and thelaminated thick plate analysis.
文摘目的:探讨慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)患者Ⅰ型胶原氨基端前肽(N-terminal propeptide of typeⅠprocollagen,PⅠNP)、Ⅰ型胶原羧基端肽β特殊序列(β-Cterminal telopeptide of typeⅠcollagen,β-CTX)水平与骨密度降低的关系。方法:选取COPD患者80例,分为COPD急性加重组40例与COPD稳定组40例,选取同期在本院体检的健康人群40例作为对照组,采用双能X射线骨密度检测仪测量所有对象的骨密度,测定并比较血清中骨代谢指标PⅠNP、β-CTX的水平。结果:COPD急性加重组与COPD稳定组骨质疏松发生率均明显高于对照组(P<0.001)。COPD急性加重组与COPD稳定组血清β-CTX水平较对照组均显著升高,且COPD急性加重组高于COPD稳定组,差异均有统计学意义(P<0.05);而COPD急性加重组与COPD稳定组血清PⅠNP水平、PⅠNP/β-CTX比值均低于对照组(P<0.01)。结论:COPD患者,尤其是急性加重期的患者,骨吸收功能异常活跃,新骨形成速度减慢,骨量丢失明显增加,从而存在较高的继发骨质疏松的风险。
文摘A Jones-Nelson model has been applied to depict nonlinearstress-strain relations of composite laminae, where mechanicalproperties were expressed by strain energy density. The nonlin- earmaterial matrix is only a function of the strain energy density. Thena material model could be conveniently applied under complex stresscondition. In this paper, by introducing large displacementstress-strain measurement and varying-Poisson's ratio idea, animproved Jones-Nelson material model is presented, where theexpanding problem of material properties and convergence problems areover- come.
基金supported by the National Natural Science Foundation of China (Grant No. 11421091)the Fundamental Research Funds for the Central Universities (Grant No. HIT.MKSTISP.2016 09)
文摘Simulation based structural reliability analysis suffers from a heavy computational burden, as each sample needs to be evaluated on the performance function, where structural analysis is performed. To alleviate the computational burden, related research focuses mainly on reduction of samples and application of surrogate model, which substitutes the performance function. However,the reduction of samples is achieved commonly at the expense of loss of robustness, and the construction of surrogate model is computationally expensive. In view of this, this paper presents a robust and efficient method in the same direction. The present method uses radial-based importance sampling (RBIS) to reduce samples without loss of robustness. Importantly, Kriging is fully used to efficiently implement RBIS. It not only serves as a surrogate to classify samples as we all know, but also guides the procedure to determine the optimal radius, with which RBIS would reduce samples to the highest degree. When used as a surrogate, Kriging is established through active learning, where the previously evaluated points to determine the optimal radius are reused. The robustness and efficiency of the present method are validated by five representative examples, where the present method is compared mainly with two fundamental reliability methods based on active learning Kriging.
