This paper presents a review of the work on fluid/structure impact based on inviscid and imcompressible liquid and irrotational flow. The focus is on the velocity potential theory together with boundary element method...This paper presents a review of the work on fluid/structure impact based on inviscid and imcompressible liquid and irrotational flow. The focus is on the velocity potential theory together with boundary element method （BEM）. Fully nonlinear boundary conditions are imposed on the unknown free surface and the wetted surface of the moving body. The review includes （1） vertical and oblique water entry of a body at constant or a prescribed varying speed, as well as free fall motion, （2） liquid droplets or column impact as well as wave impact on a body, （3） similarity solution of an expanding body. It covers two dimensional （2D）, axisymmetric and three dimensional （3D） cases. Key techniques used in the numerical simulation are outlined, including mesh generation on the multivalued free surface, the stretched coordinate system for expanding domain, the auxiliary function method for decoupling the mutual dependence of the pressure and the body motion, and treatment for the jet or the thin liquid film developed during impact.展开更多
Transferring MoS2 films from growth substrates onto target substrates is a critical issue for their practical applications. Moreover, it remains a great challenge to avoid sample degradation and substrate destruction,...Transferring MoS2 films from growth substrates onto target substrates is a critical issue for their practical applications. Moreover, it remains a great challenge to avoid sample degradation and substrate destruction, because the current transfer method inevitably employs a wet chemical etching process. We developed an etching-free transfer method for transferring MoS2 films onto arbitrary substrates by using ultrasonication. Briefly, the collapse of ultrasonication-generated microbubbles at the interface between polymer-coated MoS2 film and substrates induce sufficient force to delaminate the MoS2 films. Using this method, the MoS2 films can be transferred from all substrates （silica, mica, strontium titanate, and sapphire） and retains the original sample morphology and quality. This method guarantees a simple transfer process and allows the reuse of growth substrates, without involving any hazardous etchants. The etching-free transfer method is likely to promote broad applications of MoS2 in photodetectors.展开更多
The elastic stress fields caused by a dislocation in GexSil~ epitaxial layer on Si substrate are investigated in this work. Based on the previous results in an anisotropic bimaterial system, the image method is furthe...The elastic stress fields caused by a dislocation in GexSil~ epitaxial layer on Si substrate are investigated in this work. Based on the previous results in an anisotropic bimaterial system, the image method is further developed to determine the stress field of a dislocation in the film-substrate system under coupled condition. The film-substrate system is firstly transformed into a bimaterial system by distributing image dislocation densities on the position of the free surface. Then, the unknown image dis- location densities are solved by using boundary conditions, i.e., traction free conditions on the free surface. Numerical simula- tion focuses on the Ge0.1Si0.9/Si film-substrate system. The effects of layer thickness, position of the dislocation and crystallo- graphic orientation on the stress fields are discussed. Results reveal that both the stresses σxx,σxz at the free surface and the stress o-σx, σyy, σyz on the interface are influenced by the layer thickness, but the former is stronger. In contrast to the weak de- pendence of stress field on the crystallographic orientation the stress field was strongly affected by dislocation position. The stress fields both in the film-substrate system and bimaterial system are plotted.展开更多
基金Foundation item： Supported by the National Natural Science Foundation of China （Grant Nos. 11302057, 11302056）, the Fundamental Research Funds for the Central Universities （Grant No. HEUCF140115） and the Research Funds for State Key Laboratory of Ocean Engineering in Shanghai Jiao Tong University （Grant No. 1310）.
文摘This paper presents a review of the work on fluid/structure impact based on inviscid and imcompressible liquid and irrotational flow. The focus is on the velocity potential theory together with boundary element method （BEM）. Fully nonlinear boundary conditions are imposed on the unknown free surface and the wetted surface of the moving body. The review includes （1） vertical and oblique water entry of a body at constant or a prescribed varying speed, as well as free fall motion, （2） liquid droplets or column impact as well as wave impact on a body, （3） similarity solution of an expanding body. It covers two dimensional （2D）, axisymmetric and three dimensional （3D） cases. Key techniques used in the numerical simulation are outlined, including mesh generation on the multivalued free surface, the stretched coordinate system for expanding domain, the auxiliary function method for decoupling the mutual dependence of the pressure and the body motion, and treatment for the jet or the thin liquid film developed during impact.
基金Acknowledgements This work was financially supported by the National Natural Science Foundation of China （Nos. 51222201, 51290272, 51472008, and 51432002）, the National Basic Research Program of China （Nos. 2012CB921404, 2013CB932603, 2012CB933404, and 2011CB921903）, and the Foundation for Innovative Research Groups of the National Natural Science Foundation of China （No. 51121091）.
文摘Transferring MoS2 films from growth substrates onto target substrates is a critical issue for their practical applications. Moreover, it remains a great challenge to avoid sample degradation and substrate destruction, because the current transfer method inevitably employs a wet chemical etching process. We developed an etching-free transfer method for transferring MoS2 films onto arbitrary substrates by using ultrasonication. Briefly, the collapse of ultrasonication-generated microbubbles at the interface between polymer-coated MoS2 film and substrates induce sufficient force to delaminate the MoS2 films. Using this method, the MoS2 films can be transferred from all substrates （silica, mica, strontium titanate, and sapphire） and retains the original sample morphology and quality. This method guarantees a simple transfer process and allows the reuse of growth substrates, without involving any hazardous etchants. The etching-free transfer method is likely to promote broad applications of MoS2 in photodetectors.
基金supported by the Science and Technology on Surface Physics and Chemistry Laboratory(Grant No.SPC201106)
文摘The elastic stress fields caused by a dislocation in GexSil~ epitaxial layer on Si substrate are investigated in this work. Based on the previous results in an anisotropic bimaterial system, the image method is further developed to determine the stress field of a dislocation in the film-substrate system under coupled condition. The film-substrate system is firstly transformed into a bimaterial system by distributing image dislocation densities on the position of the free surface. Then, the unknown image dis- location densities are solved by using boundary conditions, i.e., traction free conditions on the free surface. Numerical simula- tion focuses on the Ge0.1Si0.9/Si film-substrate system. The effects of layer thickness, position of the dislocation and crystallo- graphic orientation on the stress fields are discussed. Results reveal that both the stresses σxx,σxz at the free surface and the stress o-σx, σyy, σyz on the interface are influenced by the layer thickness, but the former is stronger. In contrast to the weak de- pendence of stress field on the crystallographic orientation the stress field was strongly affected by dislocation position. The stress fields both in the film-substrate system and bimaterial system are plotted.
