The high precision assemblies with considerable radial interference should be accompanied by heating and cooling processes.However,the mechanical properties of metals are greatly affected by thermal operations.So,for ...The high precision assemblies with considerable radial interference should be accompanied by heating and cooling processes.However,the mechanical properties of metals are greatly affected by thermal operations.So,for evaluating the stress distribution and distortion of teeth profiles in a gear/shaft assembly,a transient thermal analysis is necessary for finding the change in mechanical properties.The friction on the contact surface is another important parameter in interaction of the gear with the shaft.Evaluating the gear stress and deformation fields for several modes of heat transfer and friction coefficients showed that the maximum radial or tangential stresses on contact surface of the joint may have more than 8%increase by increasing friction coefficient;while the intensity of heat transfer at cooling stage has lower effect on stress distribution.展开更多
Three types of the soil-structure interaction are used for structure analysis loaded by seismic effects. An example of the real RC building is used to demonstrate differences in the dynamic response results in the cal...Three types of the soil-structure interaction are used for structure analysis loaded by seismic effects. An example of the real RC building is used to demonstrate differences in the dynamic response results in the calculation of internal forces and displacements. Variant three options of the soil models were used as a building supporting structure. In the case of soil model A, the soil was modelled by using of equivalent stiffness values, stemming from the theory of a rigid circular disc on an elastic homogeneous half-space. Non-uniformly modelled vertical stiffness of the soil according to the Boussinesq model was used for model B. Both models A and B are characterised by the ＂averaged＂ soil model on the bases of spring constants. Model C was used for the soil better corresponding to its actual composition by the Winkler-Pasternak theory. Model C, where the actual layered soil is considered, is modelled more accurately than for the ＂averaged＂ soil of models A and B. The dynamic response of models operating with ＂averaged＂ values of rigid and soft soil layers is markedly shifted to the conservative smaller values of internal forces. The building response tbr model C in dynamic displacements is significantly higher than for the both models A and B.展开更多
This paper presents a method to create concept models for the tapered thin-walled tubes using beam elements and spring elements.Developed concept tapered beam models with different taper angles and cross sections are ...This paper presents a method to create concept models for the tapered thin-walled tubes using beam elements and spring elements.Developed concept tapered beam models with different taper angles and cross sections are compared with those detailed models through impact analyses.Important crash results are recorded and compared,and the relatively good agreement is achieved between these analyses.Concept modeling steps are illustrated in detail,and a general concept modeling method for such thin-walled tubes is summarized and presented.展开更多
Under China's innovation-driven development strategy, venture capital has become an important driving force in urban agglomeration integration and collaborative innovation. This paper uses social network analysis ...Under China's innovation-driven development strategy, venture capital has become an important driving force in urban agglomeration integration and collaborative innovation. This paper uses social network analysis to analyze spatiotemporal differences of venture capital in the Beijing-Tianjin-Hebei urban agglomeration for the period 2005–2015. A gravity model and panel data regression model are used to reveal the influencing factors on spatiotemporal differences in venture capital in the region. This study finds that there is a certain cyclical fluctuation and uneven differentiation in the venture capital network in the Beijing-Tianjin-Hebei urban agglomeration in terms of total investment, and that the three centers of venture capital(Beijing, Shijiazhuang and Tangshan) have a stimulatory effect on surrounding cities; flows of venture capital between cities display certain networking rules, but they are slow to develop and strongly centripetal; there is a strong positive correlation between levels of information infrastructure development and economic development and venture capital investment; and places with relatively underdeveloped financial environments and service industries are less able to apply the fruits of innovation and entrepreneurship and to attract funds. This study can act as a reference for the Beijing-Tianjin-Hebei urban agglomeration in building a world-class super urban agglomeration with the best innovation capabilities in China.展开更多
文摘The high precision assemblies with considerable radial interference should be accompanied by heating and cooling processes.However,the mechanical properties of metals are greatly affected by thermal operations.So,for evaluating the stress distribution and distortion of teeth profiles in a gear/shaft assembly,a transient thermal analysis is necessary for finding the change in mechanical properties.The friction on the contact surface is another important parameter in interaction of the gear with the shaft.Evaluating the gear stress and deformation fields for several modes of heat transfer and friction coefficients showed that the maximum radial or tangential stresses on contact surface of the joint may have more than 8%increase by increasing friction coefficient;while the intensity of heat transfer at cooling stage has lower effect on stress distribution.
文摘Three types of the soil-structure interaction are used for structure analysis loaded by seismic effects. An example of the real RC building is used to demonstrate differences in the dynamic response results in the calculation of internal forces and displacements. Variant three options of the soil models were used as a building supporting structure. In the case of soil model A, the soil was modelled by using of equivalent stiffness values, stemming from the theory of a rigid circular disc on an elastic homogeneous half-space. Non-uniformly modelled vertical stiffness of the soil according to the Boussinesq model was used for model B. Both models A and B are characterised by the ＂averaged＂ soil model on the bases of spring constants. Model C was used for the soil better corresponding to its actual composition by the Winkler-Pasternak theory. Model C, where the actual layered soil is considered, is modelled more accurately than for the ＂averaged＂ soil of models A and B. The dynamic response of models operating with ＂averaged＂ values of rigid and soft soil layers is markedly shifted to the conservative smaller values of internal forces. The building response tbr model C in dynamic displacements is significantly higher than for the both models A and B.
文摘This paper presents a method to create concept models for the tapered thin-walled tubes using beam elements and spring elements.Developed concept tapered beam models with different taper angles and cross sections are compared with those detailed models through impact analyses.Important crash results are recorded and compared,and the relatively good agreement is achieved between these analyses.Concept modeling steps are illustrated in detail,and a general concept modeling method for such thin-walled tubes is summarized and presented.
基金Major Program of the National Natural Science Foundation of China,No.41590842
文摘Under China's innovation-driven development strategy, venture capital has become an important driving force in urban agglomeration integration and collaborative innovation. This paper uses social network analysis to analyze spatiotemporal differences of venture capital in the Beijing-Tianjin-Hebei urban agglomeration for the period 2005–2015. A gravity model and panel data regression model are used to reveal the influencing factors on spatiotemporal differences in venture capital in the region. This study finds that there is a certain cyclical fluctuation and uneven differentiation in the venture capital network in the Beijing-Tianjin-Hebei urban agglomeration in terms of total investment, and that the three centers of venture capital(Beijing, Shijiazhuang and Tangshan) have a stimulatory effect on surrounding cities; flows of venture capital between cities display certain networking rules, but they are slow to develop and strongly centripetal; there is a strong positive correlation between levels of information infrastructure development and economic development and venture capital investment; and places with relatively underdeveloped financial environments and service industries are less able to apply the fruits of innovation and entrepreneurship and to attract funds. This study can act as a reference for the Beijing-Tianjin-Hebei urban agglomeration in building a world-class super urban agglomeration with the best innovation capabilities in China.
