The influence of the distribution of nano-pores on the mechanical properties evaluation of porous low-k films by surface acoustic waves （SAW） is studied. A theoretical SAW propagation model is set up to characterize...The influence of the distribution of nano-pores on the mechanical properties evaluation of porous low-k films by surface acoustic waves （SAW） is studied. A theoretical SAW propagation model is set up to characterize the periodic porous dielectrics by transversely isotropic symmetry. The theoretical deductions of SAW propagating in the low-k film/Si substrate layered structure are given in detail. The dispersive characteristics of SAW in differ- ent propagation directions and the effects of the Young＇s moduli E, E′ and shear modulus G′ of the films on these dispersive curves are found. Computational results show that E′ and G′ cannot be measured along the propagation direction that is perpendicular to the nano-pores＇ direction.展开更多
Wave breaking is an important process that controls turbulence properties and fluxes of heat and mass in the upper oceanic layer.A model is described for energy dissipation per unit area at the ocean surface attribute...Wave breaking is an important process that controls turbulence properties and fluxes of heat and mass in the upper oceanic layer.A model is described for energy dissipation per unit area at the ocean surface attributed to wind-generated breaking waves,in terms of ratio of energy dissipation to energy input,windgenerated wave spectrum,and wave growth rate.Also advanced is a vertical distribution model of turbulent kinetic energy,based on an exponential distribution method.The result shows that energy dissipation rate depends heavily on wind speed and sea state.Our results agree well with predictions of previous works.展开更多
The surface acoustic wave （SAW） propagating in a sample of steel is simulated by using finite element method （FEM）. The waves are excited by a load function with propagation properties such as phase velocity dispe...The surface acoustic wave （SAW） propagating in a sample of steel is simulated by using finite element method （FEM）. The waves are excited by a load function with propagation properties such as phase velocity disper- sion and wide bandwidth. A two-dimensional model consisting of surface defects loaded with a wideband 50--200 M Hz and short time 0.1 gs displacement function is investigated in the time and frequency domains. By transient dy- namic analysis, Fourier transform and dispersion calculation, snapshots of propagating wave and responses from sens- ing points are presented. It is indicated that this supervision approach is sensitive to the surface cracks and reflections.展开更多
That whether unidirectional tension changes the influence of incident angle on FSS's(frequency selective surface) electromagnetic(EM) property and whether incident angle changes the effect of unidirectional intens...That whether unidirectional tension changes the influence of incident angle on FSS's(frequency selective surface) electromagnetic(EM) property and whether incident angle changes the effect of unidirectional intension on FSS's EM property is researched.The pattern and magnitude of these changes are revealed.Firstly,the analyses for the mechanism of unidirectional tension's influence and the mechanism of the coupling between the influences of unidirectional tension and incident angle are conducted.Then,according to the mechanism of these influences,Mechanics-Electromagnetics co-analysis is conducted based on mechanics finite element method and electromagnetics finite element method.The frequency responses of the FSS which is under different unidirectional tensions and illuminated by EM wave incident at different angles are gained.The concept"unidirectional tensile sensitivity of FSS"is put forward along with two unidirectional tensile sensitivity factors.By using angular sensitivity-factor and unidirectional tensile sensitivity-factor,the influences of unidirectional tension and incident angle,which are coupled with each other,are expatiated respectively.Research results show that these influences have two sides.Meanwhile,basing on Mode Matching Method and according to the results of numerical investigation,one principle for the layout of FSS with apertures is gained.Several suggestions for further research are given.展开更多
文摘The influence of the distribution of nano-pores on the mechanical properties evaluation of porous low-k films by surface acoustic waves （SAW） is studied. A theoretical SAW propagation model is set up to characterize the periodic porous dielectrics by transversely isotropic symmetry. The theoretical deductions of SAW propagating in the low-k film/Si substrate layered structure are given in detail. The dispersive characteristics of SAW in differ- ent propagation directions and the effects of the Young＇s moduli E, E′ and shear modulus G′ of the films on these dispersive curves are found. Computational results show that E′ and G′ cannot be measured along the propagation direction that is perpendicular to the nano-pores＇ direction.
基金Supported by the National Natural Science Foundation of China(Nos. 40876013,40906008,41176011,41106012,and U0933001) and GDUPS(2010)
文摘Wave breaking is an important process that controls turbulence properties and fluxes of heat and mass in the upper oceanic layer.A model is described for energy dissipation per unit area at the ocean surface attributed to wind-generated breaking waves,in terms of ratio of energy dissipation to energy input,windgenerated wave spectrum,and wave growth rate.Also advanced is a vertical distribution model of turbulent kinetic energy,based on an exponential distribution method.The result shows that energy dissipation rate depends heavily on wind speed and sea state.Our results agree well with predictions of previous works.
基金Supported by National Natural Science Foundation of China (No. 51075296)Sate Key Laboratory of Precision Measuring Technology and Instruments Project (No. PILT1106)
文摘The surface acoustic wave （SAW） propagating in a sample of steel is simulated by using finite element method （FEM）. The waves are excited by a load function with propagation properties such as phase velocity disper- sion and wide bandwidth. A two-dimensional model consisting of surface defects loaded with a wideband 50--200 M Hz and short time 0.1 gs displacement function is investigated in the time and frequency domains. By transient dy- namic analysis, Fourier transform and dispersion calculation, snapshots of propagating wave and responses from sens- ing points are presented. It is indicated that this supervision approach is sensitive to the surface cracks and reflections.
基金the Defense Science and Technology Advance-research for Ship Industry
文摘That whether unidirectional tension changes the influence of incident angle on FSS's(frequency selective surface) electromagnetic(EM) property and whether incident angle changes the effect of unidirectional intension on FSS's EM property is researched.The pattern and magnitude of these changes are revealed.Firstly,the analyses for the mechanism of unidirectional tension's influence and the mechanism of the coupling between the influences of unidirectional tension and incident angle are conducted.Then,according to the mechanism of these influences,Mechanics-Electromagnetics co-analysis is conducted based on mechanics finite element method and electromagnetics finite element method.The frequency responses of the FSS which is under different unidirectional tensions and illuminated by EM wave incident at different angles are gained.The concept"unidirectional tensile sensitivity of FSS"is put forward along with two unidirectional tensile sensitivity factors.By using angular sensitivity-factor and unidirectional tensile sensitivity-factor,the influences of unidirectional tension and incident angle,which are coupled with each other,are expatiated respectively.Research results show that these influences have two sides.Meanwhile,basing on Mode Matching Method and according to the results of numerical investigation,one principle for the layout of FSS with apertures is gained.Several suggestions for further research are given.
