This paper presents a topology optimization approach for the surface flows on variable design domains.Via this approach,the matching between the pattern of a surface flow and the 2-manifold used to define the pattern ...This paper presents a topology optimization approach for the surface flows on variable design domains.Via this approach,the matching between the pattern of a surface flow and the 2-manifold used to define the pattern can be optimized,where the 2-manifold is implicitly defined on another fixed 2-manifold named as the base manifold.The fiber bundle topology optimization approach is developed based on the description of the topological structure of the surface flow by using the differential geometry concept of the fiber bundle.The material distribution method is used to achieve the evolution of the pattern of the surface flow.The evolution of the implicit 2-manifold is realized via a homeomorphous map.The design variable of the pattern of the surface flow and that of the implicit 2-manifold are regularized by two sequentially implemented surface-PDE filters.The two surface-PDE filters are coupled,because they are defined on the implicit 2-manifold and base manifold,respectively.The surface Navier-Stokes equations,defined on the implicit 2-manifold,are used to describe the surface flow.The fiber bundle topology optimization problem is analyzed using the continuous adjoint method implemented on the first-order Sobolev space.Several numerical examples have been provided to demonstrate this approach,where the combination of the viscous dissipation and pressure drop is used as the design objective.展开更多
Backlash-like hysteresis is one of the nonsmooth and multi-valued nonlinearities usually existing in mechanical systems. The traditional identification method is quite difficult to be used to model the systems involve...Backlash-like hysteresis is one of the nonsmooth and multi-valued nonlinearities usually existing in mechanical systems. The traditional identification method is quite difficult to be used to model the systems involved with such complex nonlinearities. In this paper, a nonsmooth recursive identification algorithm for the systems with backlash-like hysteresis is proposed. In this method, the concept of Clarke subgradient is introduced to approximate the gradients at nonsmooth points and the so-called bundle method is used to obtain the optimization search direction in nonsmooth cases. Then, a recursive algorithm based on the idea of bundle method is developed for parameter estimation. After that, the convergence analysis of the algorithm is investigated. Finally, simulation results to validate the proposed method on a simulated mechanical transmission system are presented.展开更多
Fe-Mo-Mg-O catalyst prepared by combustion method has great efficiency to grow carbon nanotubes with CVD method. Through investigation of TEM, it is found that bundles of multi-wall carbon nanotubes (MWCNT) can be got...Fe-Mo-Mg-O catalyst prepared by combustion method has great efficiency to grow carbon nanotubes with CVD method. Through investigation of TEM, it is found that bundles of multi-wall carbon nanotubes (MWCNT) can be got when the catalyst is directly used to synthesize the product in CH 4/H 2 atmosphere; however, the dispersed carbon nanotubes are obtained while the catalyst is reduced firstly in the H 2 before the synthesis. The morphology and structure of the catalysts before and after reduced are analyzed by TEM and XRD. The growth mechanism is suggeested for the formation off these two kinds of carbon nanotubes.展开更多
Theory of film condensation heat transfer(FCHT) for vapor condensed on horizontal tube bundle(HTB) is vital to many industry processes.Meanwhile,the inundation effect is the key to model the film condensation heat tra...Theory of film condensation heat transfer(FCHT) for vapor condensed on horizontal tube bundle(HTB) is vital to many industry processes.Meanwhile,the inundation effect is the key to model the film condensation heat transfer coefficient(CHTC) on HTB.This paper proposed a new experimental method,homologous method,to obtain the inundation effect precisely.Based on the requirements of the new test method,a new test facility was designed and established.Then,the superiority of homologous method for inundation effect was investigated based on experiment result and theoretic analysis.The results showed that the homogenous method can effectively control the experimental error of inundation effect,which is less than 50% of the error of CHTC,and less than 30% of the error of the inundation effect gained by routine method.The new test facility built for the homogenous method is excellent in obtaining the accurate inundation effect of film condensation on HTB.All the result is a foundation of the theoretical development of the FCHT on HTB.展开更多
基金Supported by National Natural Science Foundation of China (Grant No.51875545)Innovation Grant of Changchun Institute of Optics+2 种基金Fine Mechanics and Physics (CIOMP)CAS Project for Young Scientists in Basic Research of China (Grant No.YSBR-066)Science and Technology Development Program of Jilin Province of China (Grant No.SKL202302020)。
文摘This paper presents a topology optimization approach for the surface flows on variable design domains.Via this approach,the matching between the pattern of a surface flow and the 2-manifold used to define the pattern can be optimized,where the 2-manifold is implicitly defined on another fixed 2-manifold named as the base manifold.The fiber bundle topology optimization approach is developed based on the description of the topological structure of the surface flow by using the differential geometry concept of the fiber bundle.The material distribution method is used to achieve the evolution of the pattern of the surface flow.The evolution of the implicit 2-manifold is realized via a homeomorphous map.The design variable of the pattern of the surface flow and that of the implicit 2-manifold are regularized by two sequentially implemented surface-PDE filters.The two surface-PDE filters are coupled,because they are defined on the implicit 2-manifold and base manifold,respectively.The surface Navier-Stokes equations,defined on the implicit 2-manifold,are used to describe the surface flow.The fiber bundle topology optimization problem is analyzed using the continuous adjoint method implemented on the first-order Sobolev space.Several numerical examples have been provided to demonstrate this approach,where the combination of the viscous dissipation and pressure drop is used as the design objective.
基金supported by the National Natural Science Foundation of China (Nos. 61203108, 60971004, 61171088)the projects of the Science and Technology Commission of Shanghai (Nos. 09220503000, 10JC1412200, 09ZR1423400)the projects of Shanghai Education Commission(Nos. 11YZ92, 13YZ056)
文摘Backlash-like hysteresis is one of the nonsmooth and multi-valued nonlinearities usually existing in mechanical systems. The traditional identification method is quite difficult to be used to model the systems involved with such complex nonlinearities. In this paper, a nonsmooth recursive identification algorithm for the systems with backlash-like hysteresis is proposed. In this method, the concept of Clarke subgradient is introduced to approximate the gradients at nonsmooth points and the so-called bundle method is used to obtain the optimization search direction in nonsmooth cases. Then, a recursive algorithm based on the idea of bundle method is developed for parameter estimation. After that, the convergence analysis of the algorithm is investigated. Finally, simulation results to validate the proposed method on a simulated mechanical transmission system are presented.
文摘Fe-Mo-Mg-O catalyst prepared by combustion method has great efficiency to grow carbon nanotubes with CVD method. Through investigation of TEM, it is found that bundles of multi-wall carbon nanotubes (MWCNT) can be got when the catalyst is directly used to synthesize the product in CH 4/H 2 atmosphere; however, the dispersed carbon nanotubes are obtained while the catalyst is reduced firstly in the H 2 before the synthesis. The morphology and structure of the catalysts before and after reduced are analyzed by TEM and XRD. The growth mechanism is suggeested for the formation off these two kinds of carbon nanotubes.
基金supported by the National Natural Science Foundation of China (Grant No. 51078053)the Fundamental Research Funds for the Central Universities of China (Grant No. DUT11ZD105)
文摘Theory of film condensation heat transfer(FCHT) for vapor condensed on horizontal tube bundle(HTB) is vital to many industry processes.Meanwhile,the inundation effect is the key to model the film condensation heat transfer coefficient(CHTC) on HTB.This paper proposed a new experimental method,homologous method,to obtain the inundation effect precisely.Based on the requirements of the new test method,a new test facility was designed and established.Then,the superiority of homologous method for inundation effect was investigated based on experiment result and theoretic analysis.The results showed that the homogenous method can effectively control the experimental error of inundation effect,which is less than 50% of the error of CHTC,and less than 30% of the error of the inundation effect gained by routine method.The new test facility built for the homogenous method is excellent in obtaining the accurate inundation effect of film condensation on HTB.All the result is a foundation of the theoretical development of the FCHT on HTB.
