A reproducing kernel collocation method based on strong formulation is introduced for transient dynamics. To study the stability property of this method, an algorithm based on the von Neumann hypothesis is proposed to...A reproducing kernel collocation method based on strong formulation is introduced for transient dynamics. To study the stability property of this method, an algorithm based on the von Neumann hypothesis is proposed to predict the critical time step. A numerical test is conducted to validate the algorithm. The numerical critical time step and the predicted critical time step are in good agreement. The results are compared with those obtained based on the radial basis collocation method, and they axe in good agreement. Several important conclusions for choosing a proper support size of the reproducing kernel shape function are given to improve the stability condition.展开更多
We proposed and demonstrated the generation and transmission of 10-Gbps retum-to-zero ON/OFF keying （RZ-OOK） signal using a new technique without pulse carving at transmitter. The new technique is characterized by a...We proposed and demonstrated the generation and transmission of 10-Gbps retum-to-zero ON/OFF keying （RZ-OOK） signal using a new technique without pulse carving at transmitter. The new technique is characterized by a 3 dB built-in gain with better tolerance for chromatic dispersion in standard single mode fiber （SSMF）. Fiber Bragg grating （FBG） is used as chromatic dispersion compensating device to investigate the toler- ance of the proposed scheme. The simulation model of wavelength division multiplexing （WDM） based on OptiSystem.v.8.0 is presented. Simulation results show that there are error free transmission performance in a distance of 600 km with negligible power penalty and improved receiver sensitivity compared to conventional pulse carving approach.展开更多
The transports of the dynamic biochemical signals in the non-reversing pulsatile flows in the mixing microchannel of a Y-shaped microfluidic device are ana- lyzed. The results show that the mixing micro-channel acts a...The transports of the dynamic biochemical signals in the non-reversing pulsatile flows in the mixing microchannel of a Y-shaped microfluidic device are ana- lyzed. The results show that the mixing micro-channel acts as a low-pass filter, and the biochemical signals are nonlinearly modulated by the pulsatile flows, which depend on the biochemical signal frequency, the flow signal frequency, and the biochemical signal transporting distance. It is concluded that, the transfer characteristics of the dynamic biochemical signals, which are transported in the time-varying flows, should be carefully considered for better loading biochemical signals on the cells cultured on the bottom of the microfluidic channel.展开更多
Numerically solving 3D seismic wave equations is a key requirement for forward modeling and inversion.Here,we propose a weighted Runge-Kutta dis-continuous Galerkin(WRKDG)method for 3D acoustic and elastic wave-field ...Numerically solving 3D seismic wave equations is a key requirement for forward modeling and inversion.Here,we propose a weighted Runge-Kutta dis-continuous Galerkin(WRKDG)method for 3D acoustic and elastic wave-field mod-eling.For this method,the second-order seismic wave equations in 3D heteroge-neous anisotropic media are transformed into a first-order hyperbolic system,and then we use a discontinuous Galerkin(DG)solver based on numerical-flux formulations for spatial discretization.The time discretization is based on an implicit di-agonal Runge-Kutta(RK)method and an explicit iterative technique,which avoids solving a large-scale system of linear equations.In the iterative process,we introduce a weighting factor.We investigate the numerical stability criteria of the 3D method in detail for linear and quadratic spatial basis functions.We also present a 3D analysis of numerical dispersion for the full discrete approximation of acoustic equation,which demonstrates that the WRKDG method can efficiently suppress numerical dispersion on coarse grids.Numerical results for several different 3D models including homogeneous and heterogeneous media with isotropic and anisotropic cases show that the 3D WRKDG method can effectively suppress numerical dispersion and provide accurate wave-field information on coarse mesh.展开更多
In this study,two different methods were applied to disperse hollow silica nanoparticles(HSNP);one employed polyethylenimine(PEI)as the dispersant during the synthesis processes for preparing HSNP,while the other adde...In this study,two different methods were applied to disperse hollow silica nanoparticles(HSNP);one employed polyethylenimine(PEI)as the dispersant during the synthesis processes for preparing HSNP,while the other added PEI into suspensions of the prepared HSNP and used milling treatment to achieve the desired dispersion.It was found that adding PEI during the synthesis process of HSNP had no noticeable improvement in the dispersion,while adding PEI into suspen-sions of the prepared HSNP and utilizing milling treatment resulted in remarkable dispersion improvement.Therefore,the latter was chosen as the method in dispersing HSNP suspensions.The adsorption of PEI on the surface of HSNP and the stability of the aqueous suspensions was investigated.The results indicated that the adsorption of PEI on the surface of HSNP would increase the repulsive energy among particles,hence reducing the agglomeration of HSNP and improving the stability of the aqueous suspensions.The change of HSNP’s ■ potential after adding PEI and the rela-tionship between the adsorbed amount of PEI and pH were also investigated.展开更多
The elastic wave propagation phenomena in two-dimensional periodic beam lattices are studied by using the Bloch wave transform. The numerical modeling is applied to the hexagonal and the rectangular beam lattices, in ...The elastic wave propagation phenomena in two-dimensional periodic beam lattices are studied by using the Bloch wave transform. The numerical modeling is applied to the hexagonal and the rectangular beam lattices, in which, both the in-plane （with respect to the lattice plane） and out-of-plane waves are considered. The dispersion relations are obtained by calculating the Bloch eigenfrequencies and eigenmodes. The frequency bandgaps are observed and the influence of the elastic and geometric properties of the primitive cell on the bandgaps is studied. By analyzing the phase and the group velocities of the Bloch wave modes, the anisotropic behaviors and the dispersive characteristics of the hexagonal beam lattice with respect to the wave prop- agation are highlighted in high frequency domains. One im- portant result presented herein is the comparison between the first Bloch wave modes to the membrane and bend- ing/transverse shear wave modes of the classical equivalent homogenized orthotropic plate model of the hexagonal beam lattice. It is shown that, in low frequency ranges, the homog- enized plate model can correctly represent both the in-plane and out-of-plane dynamic behaviors of the beam lattice, its frequency validity domain can be precisely evaluated thanks to the Bloch modal analysis. As another important and original result, we have highlighted the existence of the retro- propagating Bloch wave modes with a negative group veloc- ity, and of the corresponding ＂retro-propagating＂ frequency bands.展开更多
以端乙烯基硅油、低含氢硅油为基料,甲基乙烯基硅氧烷-铂配合物为催化剂,添加导热填料三氧化二铝和阻燃填料氢氧化铝,制备了加成型导热阻燃灌封胶。比较了捏合机和高速分散机在室温及加热条件下对导热阻燃灌封胶性能的影响。结果表明,...以端乙烯基硅油、低含氢硅油为基料,甲基乙烯基硅氧烷-铂配合物为催化剂,添加导热填料三氧化二铝和阻燃填料氢氧化铝,制备了加成型导热阻燃灌封胶。比较了捏合机和高速分散机在室温及加热条件下对导热阻燃灌封胶性能的影响。结果表明,捏合机在130℃条件下处理得到的灌封胶黏度(6 000 m Pa·s)优于捏合机在室温处理的灌封胶黏度(8 000 m Pa·s);采用表面预先处理过的三氧化二铝和氢氧化铝作为填料,经高速分散机制备的灌封胶其力学性能(拉伸强度1.31 MPa,拉断伸长率69%)优于捏合机得到的灌封胶(拉伸强度1.17 MPa,拉断伸长率47%),但是经捏合机处理得到的灌封胶的热导率优于高速分散机处理的。如果填料的表面处理是在制备灌封胶的过程中,和捏合机相比,高速分散机制备的灌封胶具有更优的黏度和力学性能。展开更多
基金Project supported by the Western Transport Technical Project of Ministry of Transport of China(No. 2009318000046)
文摘A reproducing kernel collocation method based on strong formulation is introduced for transient dynamics. To study the stability property of this method, an algorithm based on the von Neumann hypothesis is proposed to predict the critical time step. A numerical test is conducted to validate the algorithm. The numerical critical time step and the predicted critical time step are in good agreement. The results are compared with those obtained based on the radial basis collocation method, and they axe in good agreement. Several important conclusions for choosing a proper support size of the reproducing kernel shape function are given to improve the stability condition.
文摘We proposed and demonstrated the generation and transmission of 10-Gbps retum-to-zero ON/OFF keying （RZ-OOK） signal using a new technique without pulse carving at transmitter. The new technique is characterized by a 3 dB built-in gain with better tolerance for chromatic dispersion in standard single mode fiber （SSMF）. Fiber Bragg grating （FBG） is used as chromatic dispersion compensating device to investigate the toler- ance of the proposed scheme. The simulation model of wavelength division multiplexing （WDM） based on OptiSystem.v.8.0 is presented. Simulation results show that there are error free transmission performance in a distance of 600 km with negligible power penalty and improved receiver sensitivity compared to conventional pulse carving approach.
基金Project supported by the National Natural Science Foundation of China(Nos.11172060 and11672065)
文摘The transports of the dynamic biochemical signals in the non-reversing pulsatile flows in the mixing microchannel of a Y-shaped microfluidic device are ana- lyzed. The results show that the mixing micro-channel acts as a low-pass filter, and the biochemical signals are nonlinearly modulated by the pulsatile flows, which depend on the biochemical signal frequency, the flow signal frequency, and the biochemical signal transporting distance. It is concluded that, the transfer characteristics of the dynamic biochemical signals, which are transported in the time-varying flows, should be carefully considered for better loading biochemical signals on the cells cultured on the bottom of the microfluidic channel.
基金supported by the Hainan Provincial Natural Science Foundation of China(Grant No.418QN205)the National Natural Science Foundation of China(Grant Nos.41604090,91730306)+1 种基金the National Key R&D Program on Monitoring,Early Warning and Prevention of Major Natural Disaster(Grant No.2017YFC1500301)by the Statoil Company(Contract No.4503294711).
文摘Numerically solving 3D seismic wave equations is a key requirement for forward modeling and inversion.Here,we propose a weighted Runge-Kutta dis-continuous Galerkin(WRKDG)method for 3D acoustic and elastic wave-field mod-eling.For this method,the second-order seismic wave equations in 3D heteroge-neous anisotropic media are transformed into a first-order hyperbolic system,and then we use a discontinuous Galerkin(DG)solver based on numerical-flux formulations for spatial discretization.The time discretization is based on an implicit di-agonal Runge-Kutta(RK)method and an explicit iterative technique,which avoids solving a large-scale system of linear equations.In the iterative process,we introduce a weighting factor.We investigate the numerical stability criteria of the 3D method in detail for linear and quadratic spatial basis functions.We also present a 3D analysis of numerical dispersion for the full discrete approximation of acoustic equation,which demonstrates that the WRKDG method can efficiently suppress numerical dispersion on coarse grids.Numerical results for several different 3D models including homogeneous and heterogeneous media with isotropic and anisotropic cases show that the 3D WRKDG method can effectively suppress numerical dispersion and provide accurate wave-field information on coarse mesh.
基金supported by the National Natural Science Foundation of China(Grant Nos.20506001 and 20236020)the Program for New Century Excellent Talents in University(Grant No.NCET-04-0123)Beijing Municipal Commission of Education(Grant No.JD100100403).
文摘In this study,two different methods were applied to disperse hollow silica nanoparticles(HSNP);one employed polyethylenimine(PEI)as the dispersant during the synthesis processes for preparing HSNP,while the other added PEI into suspensions of the prepared HSNP and used milling treatment to achieve the desired dispersion.It was found that adding PEI during the synthesis process of HSNP had no noticeable improvement in the dispersion,while adding PEI into suspen-sions of the prepared HSNP and utilizing milling treatment resulted in remarkable dispersion improvement.Therefore,the latter was chosen as the method in dispersing HSNP suspensions.The adsorption of PEI on the surface of HSNP and the stability of the aqueous suspensions was investigated.The results indicated that the adsorption of PEI on the surface of HSNP would increase the repulsive energy among particles,hence reducing the agglomeration of HSNP and improving the stability of the aqueous suspensions.The change of HSNP’s ■ potential after adding PEI and the rela-tionship between the adsorbed amount of PEI and pH were also investigated.
文摘The elastic wave propagation phenomena in two-dimensional periodic beam lattices are studied by using the Bloch wave transform. The numerical modeling is applied to the hexagonal and the rectangular beam lattices, in which, both the in-plane （with respect to the lattice plane） and out-of-plane waves are considered. The dispersion relations are obtained by calculating the Bloch eigenfrequencies and eigenmodes. The frequency bandgaps are observed and the influence of the elastic and geometric properties of the primitive cell on the bandgaps is studied. By analyzing the phase and the group velocities of the Bloch wave modes, the anisotropic behaviors and the dispersive characteristics of the hexagonal beam lattice with respect to the wave prop- agation are highlighted in high frequency domains. One im- portant result presented herein is the comparison between the first Bloch wave modes to the membrane and bend- ing/transverse shear wave modes of the classical equivalent homogenized orthotropic plate model of the hexagonal beam lattice. It is shown that, in low frequency ranges, the homog- enized plate model can correctly represent both the in-plane and out-of-plane dynamic behaviors of the beam lattice, its frequency validity domain can be precisely evaluated thanks to the Bloch modal analysis. As another important and original result, we have highlighted the existence of the retro- propagating Bloch wave modes with a negative group veloc- ity, and of the corresponding ＂retro-propagating＂ frequency bands.
文摘以端乙烯基硅油、低含氢硅油为基料,甲基乙烯基硅氧烷-铂配合物为催化剂,添加导热填料三氧化二铝和阻燃填料氢氧化铝,制备了加成型导热阻燃灌封胶。比较了捏合机和高速分散机在室温及加热条件下对导热阻燃灌封胶性能的影响。结果表明,捏合机在130℃条件下处理得到的灌封胶黏度(6 000 m Pa·s)优于捏合机在室温处理的灌封胶黏度(8 000 m Pa·s);采用表面预先处理过的三氧化二铝和氢氧化铝作为填料,经高速分散机制备的灌封胶其力学性能(拉伸强度1.31 MPa,拉断伸长率69%)优于捏合机得到的灌封胶(拉伸强度1.17 MPa,拉断伸长率47%),但是经捏合机处理得到的灌封胶的热导率优于高速分散机处理的。如果填料的表面处理是在制备灌封胶的过程中,和捏合机相比,高速分散机制备的灌封胶具有更优的黏度和力学性能。
